Mechanisms of impulsivity in bipolar disorder and related illness

Error monitoring and response inhibition in adolescents with bipolar disorders: An ERP study

Cognitive control develops throughout adolescence, a high-risk period for bipolar disorders (BD) onset. Despite neurobehavioral abnormalities in adults with BD, there is minimal research investigating deviations in cognitive control in adolescents with BD. Cognitive control involves numerous processes. Identifying the specific neural abnormalities in adolescent BD could provide precise targets for novel interventions that improve illness outcomes. The present study administered a Go/No-Go (GNG) task to 98 adolescents (44 BD; 54 controls) to activate response inhibition and error processes and recorded EEG for event-related potentials (ERPs) analysis. Stimulus-locked N2 and P3 (response inhibition) and response-locked error-related negativity (ERN; early error detection) and error positivity (Pe; conscious error detection) were analyzed. Adolescents with BD had attenuated Pe mean amplitudes following failed inhibition trials. There were no group differences in other ERP amplitudes, including N2, P3, and ERN. The pattern of findings implicates conscious error detection impairment in adolescents with BD, without support for deficits in more automatic, earlier error detection. Impaired conscious error detection in adolescents with BD may be an early expression of BD pathophysiology and a possible intervention target for cognitive rehabilitation. Further studies are needed to examine Pe in BD across the lifetime.

Relationship between early traumatic experiences and emotional regulation skills in major depressive and bipolar disorders

Childhood trauma can cause deficits in emotional regulation. However, few studies have investigated childhood trauma and emotional regulation skills in patients with mood disorders. We aimed to investigate how childhood trauma and Emotion Regulation Skills Questionnaire (ERSQ) scores are associated with mood disorders.This study included 779 patients with mood disorders (major depressive disorder [MDD, n = 240], bipolar I disorder [BDI, n = 121], and bipolar II disorder [BDII, n = 418]). We used their Childhood Trauma Questionnaire-Short Form (CTQ) and ERSQ scores for the evaluation.The between-group differences in CTQ and ERSQ scores were examined. The CTQ and ERSQ total scores were negatively correlated. Among the CTQ subscales, emotional neglect showed a significant correlation with the ERSQ total score, whereas acceptance and tolerance showed higher negative correlations with the CTQ than with the other ERSQ subscales. The negative relationship between emotional regulation and childhood trauma varied significantly depending on the group, with the BDI group showing a more prominent association than the other groups.Based on various mood disorders, we observed associations between childhood trauma and emotional regulation skills. Consequently, our study offers notable insights for future research on the impact of childhood trauma on ERSQ.

Transcranial Infrared Laser Stimulation Improves Cognition in Older Bipolar Patients: Proof of Concept Study

This is the first study to examine if transcranial infrared laser stimulation (TILS) improves cognition in older euthymic bipolar patients, who exhibit greater cognitive decline than is expected for age-matched controls. TILS is a non-invasive novel form of photobiomodulation that augments prefrontal oxygenation and improves cognition in young adults by upregulating the mitochondrial respiratory enzyme cytochrome-c-oxidase. We used a crossover sham-controlled design to examine if TILS to bilateral prefrontal cortex produces beneficial effects on cognition in 5 euthymic bipolar patients (ages 60-85). We measured cognitive flexibility, verbal fluency, working memory, sustained attention and impulsivity with tasks that have been shown to differentiate between healthy older adults and older bipolar adults. We found TILS-induced improvements in cognitive performance on the tasks that measure cognitive flexibility and impulsivity, after 5 weekly sessions of TILS. We concluded that TILS appeared both safe and effective in helping alleviate the accelerated cognitive decline present in older bipolar patients.

A Multimethod Examination of Sensitivity to Reward and Sensitivity to Punishment in Bipolar Disorder and Alcohol Dependence: Results from a 2 × 2 Factorial Design

INTRODUCTION

Shared neurobehavioral characteristics of bipolar disorder (BD) and alcohol dependence (AD), including heightened sensitivity to reward (SR), may account for high rates of BD and AD co-occurrence (BD + AD). However, empirical research is lacking. The present multimethod investigation examined SR and sensitivity to punishment (SP) among these patient groups using a reliable and well-validated self-report questionnaire of SR and SP along with a laboratory task specifically designed to distinguish SR and SP activation.

METHODS

One-hundred participants formed 4 groups: BD + AD (n = 40), BD (n = 18), AD (n = 25), and healthy controls (n = 17). Clinical interviews were administered, and participants completed the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSR-Q) and the Point Score Reaction Test behavioral task. Pearson correlations, hierarchical linear regression, and 2 × 2 factorial general linear modeling with Bonferroni-corrected pairwise comparisons were performed.

RESULTS

BD and AD main effects were significant on self-reported SR and SP; however, BD × AD interactions were not. BD + AD individuals were significantly higher on self-reported SR than BD and AD individuals, yet all clinical groups were similar on SP. Behavioral response times did not distinguish groups nor did they associate with self-report data.

DISCUSSION/CONCLUSION

BD and AD had additive, rather than interactive, effects on self-reported SR and SP. The methods employed, paired with their application to the present sample, may account for a lack of positive findings with behavioral data.

Decreased motor impulsivity following chronic lithium treatment in male rats is associated with reduced levels of pro-inflammatory cytokines in the orbitofrontal cortex

Lithium's efficacy in reducing both symptom severity in bipolar disorder (BD) and suicide risk across clinical populations may reflect its ability to reduce impulsivity. Changes in immune markers are associated with BD and suicidality yet their exact role in symptom expression remains unknown. Evidence also suggests that lithium may decrease levels of pro-inflammatory cytokines in the periphery and central nervous system, and that such changes are related to its therapeutic efficacy. However, issues of cause and effect are hard to infer from clinical data alone. Here, we investigated the effects of chronic dietary lithium treatment on rats' performance of the 5-Choice Serial Reaction Time Task (5CSRTT), a well-validated operant behavioural task measuring aspects of impulsivity, attention and motivation. Male Long-Evans rats received a diet supplemented with 0.3% LiCl (n = 13), or the equivalent control diet (n = 16), during behavioural testing. Blood and brain tissue samples were assayed for a wide range of cytokines once any changes in impulsivity became significant. After 12 weeks, chronic lithium treatment reduced levels of motor impulsivity, as indexed by premature responses in the 5CSRTT; measures of sustained attention and motivation were unaffected. Plasma levels of IL-1β, IL-10 and RANTES (CCL-5) were reduced in lithium-treated rats at this time point. IL-1β, IL-6 and RANTES were also reduced selectively within the orbitofrontal cortex of lithium-treated rats, whereas cytokine levels in the medial prefrontal cortex and nucleus accumbens were comparable with control subjects. These results are consistent with the hypothesis that lithium may improve impulse control deficits in clinical populations by minimising the effects of pro-inflammatory signalling on neuronal activity, particularly within the orbitofrontal cortex.

Resilience and insight in euthymic patients with bipolar disorder

BACKGROUND

The relationship between resilience and insight may be of potential importance for coping with stress in bipolar disorder (BD). The aim of this study was to investigate if there was a relation between insight and resilience in euthymic patients with BD and also to analyze the associations between resilience, impulsivity, aggression, alcohol use and affective temperament.

METHODS

142 patients with BD type I in remission period were involved. Resilience Scale for Adults-Turkish version, Schedule for Assessment of Insight, Temperament Evaluation of Memphis, Pisa, Paris and San Diego Autoquestionnaire, Barratt Impulsiveness Scale, Buss-Perry Aggression Questionnaire, Michigan Alcoholism Screening Test were used.

RESULTS

Total insight scores were negatively correlated with the scores of perception of future. As distinct from other subscales of resilience, family cohesion had independent significant associations with insight in relabelling of psychotic experiences and attention impulsivity. There was no relationship between total insight and total resilience scores. Resilience scores were negatively correlated with number of depressive episodes and number of suicide attempts. Degree of aggression, degree of impulsivity, scores of depressive and hyperthymic temperament significantly predicted resilience.

LIMITATIONS

Recruitment of patients from a tertiary centre limits the generalizability of the findings.

CONCLUSIONS

Better insight was related to negative perception of the future and did not have significant associations with total resilience. Number of depressive episodes, number of past suicide attempts correlated with resilience, emphasizing the importance of interventions to increase resilience in BD.

Delay discounting and reward sensitivity in a 2 × 2 study of bipolar disorder and alcohol dependence

BACKGROUND AND AIMS

Separate studies have shown increased delay discounting in people with bipolar disorder (BD) and people with alcohol dependence (AD) relative to people without mental health problems. Delay discounting was compared in people with no mental health problems, AD, BD and AD plus BD. Associations of delay discounting with self-reported impulsivity and reward sensitivity were also assessed.

DESIGN

The study was a two-by-two factorial comparative observational design.

SETTING

Data were collected at baseline diagnostic visits as part of a neuroimaging study at a medical university in South Carolina, USA.

PARTICIPANTS

Twenty-two BD + AD, 33 BD, 28 AD and 27 people without mental health problems participated.

MEASUREMENTS

Diagnostic and clinician-rated symptom measures, self-report questionnaires and a computerized delay discounting task were administered. Two-by-two general linear univariate models were tested to examine between-group differences on discounting rates, and bivariate correlations and hierarchical regression analyses were performed to examine associations between discounting rates and self-reported reward sensitivity and impulsivity.

FINDINGS

There was a significant main effect of AD (P = 0.006, η2  = 0.068). The main effect of BD and the BD × AD interaction terms were non-significant (P ≥ 0.293, η2  ≤ 0.010). Reward sensitivity and impulsivity were not significantly associated with discounting rates after adjustment for the other (P ≥ 0.089).

CONCLUSIONS

People with alcohol dependence appear to have higher delay discounting, while previously found associations between bipolar disorder and delay discounting may be secondary to alcohol use disorder.

Steeper aging-related declines in cognitive control processes among adults with bipolar disorders

BACKGROUND

Little is known about the specificity of executive functioning (EF) decline in older adults with bipolar disorders (OABD), or the impact of bipolar disorders (BD) on the timing and slope of age-related declines in EF processes implicated in both BD etiology and normative aging-cognitive control (CC). This cross-sectional study investigated age-related CC decline in BD.

METHODS

Participants were 43 adults with BD (M age = 61.5, SD = 15.8; 86% male) and 45 Controls (M age = 65.2, SD = 12.2; 98% male). Two-way ANOVAs examined the effects of median-age-split and diagnostic groups on cognitive processes with established BD deficits-CC processes (mental flexibility and response inhibition), verbal learning, and verbal fluency.

RESULTS

The median-split-age-by-diagnostic-group interaction was significant for mental flexibility; OABD performed significantly worse than younger adults with BD and younger and older Controls. Exploratory multivariate adaptive regression spline characterized non-linear nature of aging-slope changes in mental flexibility for each diagnostic group, yielding an inflection point at older age and steeper subsequent decline in OABD versus Controls.

LIMITATIONS

This study is limited by a small sample (particularly for select neuropsychological measures) of mostly Caucasian men and BD diagnoses based on clinical interview and medical records review.

CONCLUSIONS

Compared to healthy older adults, OABD showed steeper age-related decline in mental flexibility-select EF processes that depend on the integrity of the CC system. Preliminary evidence links CC integrity to daily functioning in OABD; accelerated aging decline in CC may pose a mechanism for high risk of functional impairment and dementia in OABD.

Efficacy and Safety of Atypical Antipsychotics in Bipolar Disorder With Comorbid Substance Dependence: A Systematic Review

OBJECTIVES

Bipolar disorder (BD) patients with a comorbid substance use disorder (SUD) are notoriously difficult to treat. Atypical antipsychotics (AAPs) are widely prescribed in BD, but their efficacy in patients with comorbid SUD is still debated. The aim of the present article is to systematically review the literature findings on the efficacy and safety of AAPs in BD patients with comorbid SUD.

METHODS

We searched PubMed to identify original studies focused on the treatment of dual diagnosed BD with AAPs.

RESULTS

Ten articles met our inclusion/exclusion criteria, involving a total of 969 subjects, 906 affected by BD and 793 with comorbid SUD: 4 were randomized controlled trials, 4 were open label trials and 2 were observational studies, published between 2002 and 2017. The most commonly abused substances were alcohol and cocaine. The AAPs used to treat patients were quetiapine (n = 337), asenapine (n = 119), olanzapine (n = 80), risperidone (n = 62), and aripiprazole (n = 48). In terms of safety, AAPs were usually well tolerated. Atypical antipsychotics were usually efficacious on acute mood symptoms, whereas their impact on substance-related issues was reported only in those studies without a placebo comparison.

CONCLUSIONS

According to our results, even though AAPs are widely used and efficacious in treating the clinical symptoms of BD, there are not enough data to suggest their adjunctive benefit on craving and substance consumption.

Linking Cognitive Measures of Response Inhibition and Reward Sensitivity to Trait Impulsivity

Impulsivity is regarded as a multifaceted construct that comprises two dimensions: rapid-response impulsivity and reward-delay impulsivity. It is unclear, however, which aspects of trait impulsivity, as assessed by self-report measures are related to rapid-response impulsivity and/or to reward-delay impulsivity, as different results have been reported in studies using both self-report and cognitive measures. This study aimed to directly relate self-report measures of impulsivity to cognitive measures of impulsivity in individuals at low- or high-levels on two impulsivity dimensions, specifically rapid-response impulsivity and reward-delay impulsivity. Participants were classified into high- or low-impulsivity groups based on (1) level of rapid-response impulsivity (determined by BIS-11 Motor subscale scores); (2) level of reward-delay impulsivity (determined by BIS/BAS subscale scores); and (3) a combination of rapid-response impulsivity and reward-delay impulsivity levels. Impulsivity was assessed using Go/No-Go, Stop-Signal and Delay-Discounting tasks and self-report measures. The high rapid-response impulsivity group showed significantly higher reward-delay impulsivity on both, the Delay-Discounting tasks and on self-report measures assessing reward-delay impulsivity, than the low-risk group. Based on the level of reward-delay impulsivity, the high reward-delay impulsivity group scored significantly higher on task-based (cognitive) and self-report measures assessing rapid-response inhibition than the low reward-delay impulsivity group. Combining both dimensions of impulsivity showed that the high-impulsivity group performed significantly worse in rapid-response paradigms and temporally discounted significantly more impulsively than the low-impulsivity group. Thus, combined impulsivity factors provide better assessment of impulsivity than each dimension alone. In conclusion, robust differences in impulsivity can be identified in non-clinical young adults.

Asenapine in the management of impulsivity and aggressiveness in bipolar disorder and comorbid borderline personality disorder: an open-label uncontrolled study

Borderline personality disorder (BPD) often co-occurres with bipolar disorder (BD). Impulsivity and aggressiveness represent core shared features and their pharmacological management is mainly based on mood stabilizers and antipsychotics, although scarce evidence is available for this context of comorbidity. The aim of the present study was to evaluate the role of Asenapine as an adjunctive drug for reducing aggressiveness and impulsivity in a sample of Italian BD type I outpatients with or without a comorbid BPD. This was an observational 12-week open-label uncontrolled clinical study carried out from April to October 2014 in two psychiatric clinics in Sicily. Each patient was treated with asenapine at two dose options, 5 mg (twice daily) or 10 mg (twice daily), and concomitant ongoing medications were not discontinued. We measured impulsivity using the Barratt Impulsiveness Scale (BIS) and aggressiveness using the Aggressive Questionnaire (AQ). For the analysis of our outcomes, patients were divided into two groups: with or without comorbid BPD. Adjunctive therapy was associated with a significant decrease of BIS and AQ overall scores in the entire bipolar sample. Yet, there was no significant difference in BIS and AQ reductions between subgroups. Using a regression model, we observed that concomitant BPD played a negative role on the Hostility subscale and overall AQ score variations; otherwise, borderline co-diagnosis was related positively to the reduction of physical aggression. According to our post-hoc analysis, global aggressiveness scores are less prone to decrease in patients with a dual diagnosis, whereas physical aggressiveness appears to be more responsive to the add-on therapy in patients with comorbidity.

Effects of Suvorexant, a Dual Orexin/Hypocretin Receptor Antagonist, on Impulsive Behavior Associated with Cocaine

Hypothalamic hypocretin (orexin) peptides mediate arousal, attention, and reward processing. Fibers containing orexins project to brain structures that govern motivated behavior, including the ventral tegmental area (VTA). A number of psychiatric conditions, including attention deficit hyperactivity disorder (ADHD) and substance use disorders, are characterized by deficits in impulse control, however the relationship between orexin and impulsive behavior is incompletely characterized. The effects of systemic or centrally administered orexin receptor (OXR) antagonists on measures of impulsive-like behavior in rats were evaluated using the five-choice serial reaction time task (5-CSRTT) and delay discounting procedures. These paradigms were also used to test the capacity of OXR antagonists to attenuate acute cocaine-evoked impulsivity. Finally, immunohistochemistry and calcium imaging were used to assess potential cellular mechanisms by which OXR blockade may influence motor impulsivity. Suvorexant, a dual (OX_1/2R) orexin receptor antagonist, reduced cocaine-evoked premature responses in 5-CSRTT when administered systemically or directly into VTA. Neither suvorexant nor OX₁R- or OX₂R-selective compounds (SB334867 or TCS-OX2-29, respectively) altered delay discounting. Finally, suvorexant did not alter Fos-immunoreactivity within tyrosine hydroxylase-immunolabeled neurons of VTA, but did attenuate cocaine- and orexin-induced increases in calcium transient amplitude within neurons of VTA. Results from the present studies suggest potential therapeutic utility of OXR antagonists in reducing psychostimulant-induced motor impulsivity. These findings also support the view that orexin transmission is closely involved in executive function in normal and pathological conditions.

Impulsivity is associated with blood pressure and waist circumference among adolescents with bipolar disorder

OBJECTIVE

Cardiovascular risk factors (CVRFs) and impulsivity are common in bipolar disorder (BD), and CVRFs are also linked with impulsivity through a number of mechanisms, both behavioral and biological. This study examines the association between CVRFs and impulsivity in adolescents with BD.

METHODS

Subjects were 34 adolescents with BD and 35 healthy control (HC) adolescents. CVRFs were based on International Diabetes Federation metabolic syndrome criteria (triglycerides, high-density lipoprotein cholesterol, waist circumference, blood pressure (BP) and glucose). Impulsivity was measured using the computerized Cambridge Gambling Task (CGT). Analyses controlled for age, IQ, lifetime attention deficit hyperactivity disorder, and current antipsychotic use.

RESULTS

Adolescents with BD had higher diastolic BP (73.36 ± 9.57 mmHg vs. 67.91 ± 8.74 mmHg, U = 401.0, p = 0.03), higher triglycerides (1.13 ± 0.60 mmol/L vs. 0.78 ± 0.38 mmol/L, U = 373.5, p = 0.008), and were more likely to meet high-risk criteria for waist circumference (17.6% vs. 2.9%, p = 0.04) vs. HC. Within the BD group, CGT sub-scores were correlated with CVRFs. For example, overall proportion bet was positively correlated with systolic (r = 0.387, p = 0.026) and diastolic (ρ = 0.404, p = 0.020) BP. Quality of decision-making was negatively correlated with systolic BP (ρ = -0.401, p = 0.021) and waist circumference (ρ = -0.534, p = 0.003). Significant interactions were observed, such that BD diagnosis moderates the relationship between both waist circumference and BP with CGT sub-scores.

CONCLUSION

BP and waist circumference are associated with impulsivity in BD adolescents, but not in HC adolescents. Future studies are warranted to determine temporality and to evaluate whether optimizing CVRFs improves impulsivity among BD adolescents.

Impulsivity in bipolar disorders in a Tunisian sample

Impulsivity as a trait characteristic is increased in bipolar disorder and may be a core factor of the illness. The objectives of our work are to evaluate the level of impulsivity among patients with bipolar disorder and to study its relation with mood state, alcohol misuse, suicide attempts and other socio-demographic and clinical factors. We measured impulsivity in 60 subjects with bipolar disorder in relationship to socio-demographic and clinical variables. The subjects completed Data included socio-demographic details and clinical variables, the Barratt Impulsiveness Scale (BIS-11) in an Arabic version to assess impulsivity, The Mini International Neuropsychiatric Interview "MINI" version 05 to screen for alcohol abuse or dependence and mood graphic rate scale (MGRS) to evaluate mood state. Our results show that the mean score of BIS-11 was 71.5. Fifty-five per cent of the patients had a high level of impulsiveness. No differences were found relating to mood state. Impulsivity was related to Male gender, lower educational level, early age of onset, smoking, alcohol and drug misuse and prior suicide attempts. The treatment of patients with BD should consider to reduce impulsivity to improve morbidity.

Associations of age with reward delay discounting and response inhibition in adolescents with bipolar disorders

OBJECTIVES

Bipolar disorders' (BD) onset before age 18 is a potential marker for a more severe illness course. Adolescence is also a period of significant normative maturation of inhibitory control and reward-relevant decision-making processes, such as decreased delay discounting (i.e., decreased preference for smaller, immediate versus larger, delayed rewards). Adults with BD exhibit elevated delay discounting rates. Very little is known about developmental changes in delay discounting in adolescents with BD, or about associations between inhibitory control and delay discounting in BD. The present study addresses these questions.

METHODS

The sample included 78 participants, ages 13 to 23, with BD or without history of mental illness. Group differences and group by age interaction effects on delay discounting (32 BD, 32 controls with valid responses), probability discounting (34 BD, 37 controls) and inhibitory control indices (34 BD, 38 controls) were assessed.

RESULTS

Among healthy controls, less discounting of delayed rewards was associated with older age, whereas adolescents with BD did not show age-related associations. There were no group differences in probability discounting or inhibitory control.

LIMITATIONS

The cross-sectional nature of the study cannot fully rule out the less likely interpretation of group differences in cohort effects.

CONCLUSIONS

The lack of age-related improvement in delay tolerance in BD suggests disrupted development of executive control processes within reward contexts, which in turn may contribute to understanding more severe course of pediatric onset BD. Longitudinal studies are needed to examine delay discounting in relation to maturation of neural reward systems among adolescents with BD.

Eye Movement in Unipolar and Bipolar Depression: A Systematic Review of the Literature

BACKGROUND

The analysis of eye movements (EM) by eye-tracking has been carried out for several decades to investigate mood regulation, emotional information processing, and psychomotor disturbances in depressive disorders.

METHOD

A systematic review of all English language PubMed articles using the terms "saccadic eye movements" OR "eye-tracking" AND "depression" OR "bipolar disorders" was conducted using PRISMA guidelines. The aim of this review was to characterize the specific alterations of EM in unipolar and bipolar depression.

RESULTS

Findings regarding psychomotor disturbance showed an increase in reaction time in prosaccade and antisaccade tasks in both unipolar and bipolar disorders. In both disorders, patients have been reported to have an attraction for negative emotions, especially for negative pictures in unipolar and threatening images in bipolar disorder. However, the pattern could change with aging, elderly unipolar patients disengaging key features of sad and neutral stimuli. METHODological limitations generally include small sample sizes with mixed unipolar and bipolar depressed patients.

CONCLUSION

Eye movement analysis can be used to discriminate patients with depressive disorders from controls, as well as patients with bipolar disorder from patients with unipolar depression. General knowledge concerning psychomotor alterations and affective regulation strategies associated with each disorder can also be gained thanks to the analysis. Future directions for research on eye movement and depression are proposed in this review.

Increased impulsivity as a vulnerability marker for bipolar disorder: evidence from self-report and experimental measures in two high-risk populations

BACKGROUND

Heightened impulsivity has been suggested as a possible risk factor for bipolar disorder (BD). However, studies on high-risk populations are scarce and have mainly focused on individuals with a genetic risk. The present study investigated two high-risk samples for BD with regard to several aspects of the impulsivity construct.

METHODS

Unaffected relatives of BD patients (genetically defined high-risk group, N=29) and participants scoring high on the Hypomanic Personality Scale (psychometrically defined high-risk sample, N=25) were being compared to respective control groups (N=27 and N=25) using a multi-method approach. Participants were accessed on the Barratt Impulsiveness Scale-11 (BIS-11, trait impulsivity), the Stop Signal Task (response inhibition), and the Cambridge Gambling Task (impulsive behavior in decision-making processes).

RESULTS

Both high-risk groups reported heightened impulsivity on the BIS-11, as well as impulsive decision-making, whereas no significant group differences in response inhibition were observed.

LIMITATIONS

Limitations were the lack in specificity of the results for BD and the cross-sectional study design, which does not allow conclusions about the influence of impulsivity on the development of or resilience for BD in risk groups.

CONCLUSIONS

Our findings support the assumption that increased trait impulsivity and impulsive decision-making are a vulnerability marker for and an endophenotype of BD.

Impulsivity in bipolar and substance use disorders

BACKGROUND

Bipolar disorder (BD) is commonly associated with increased impulsivity, particularly during manic and depressed episodes; also impulsivity remains elevated during euthymic phases. Impulsivity is also a factor in the initiation and maintenance of substance use disorders (SUD). Impulsivity can predispose to substance abuse or can result from it. Impulsivity appears to be relatively independent of mood state and is higher in individuals with past substance use. Thus, we wanted to compare the impulsivity of BD and SUD closely associated with impulsivity and identify potential differences.

METHODS

Impulsivity was evaluated by the Barratt Impulsiveness Scale (BIS-11A), in 35 bipolar interepisode disorder male patients without comorbid substance use disorder and 40 substance use disorder male patients. The BIS-11A mean scores for the two groups were compared through one-way between-groups ANOVA.

RESULTS

There was no difference between the BD and substance use disorder groups on total and subscale attentional, motor impulsivity measures. However, for the male patients there was difference on the nonplanning subscale. The male BD patient group scored higher than the male substance use disorder patient group regarding nonplanning impulsivity.

CONCLUSIONS

Our results replicate the findings that interepisode BD and substance use disorder patients both have increased total impulsivity; furthermore, the findings also indicate that trait impulsivity is not completely the same in subscales. Both groups were similar on attention and motor impulsivity subscales; however, on the nonplanning subscale, BD patients were more impulsive than the substance use disorder patients.

Disturbed anterior prefrontal control of the mesolimbic reward system and increased impulsivity in bipolar disorder

Bipolar disorder (BD) is characterized by recurrent mood episodes ranging from severe depression to acute full-blown mania. Both states of this severe psychiatric disorder have been associated with alterations of reward processing in the brain. Here, we present results of a functional magnetic resonance imaging (fMRI) study on the neural correlates and functional interactions underlying reward gain processing and reward dismissal in favor of a long-term goal in bipolar patients. Sixteen medicated patients diagnosed with bipolar I disorder, euthymic to mildly depressed, and sixteen matched healthy controls performed the 'desire-reason dilemma' (DRD) paradigm demanding rejection of priorly conditioned reward stimuli to successfully pursue a superordinate goal. Both groups exhibited significant activations in reward-related brain regions, particularly in the mesolimbic reward system. However, bipolar patients showed reduced neural responses of the ventral striatum (vStr) when exploiting a reward stimulus, and exhibited a decreased suppression of the reward-related activation of the mesolimbic reward system while having to reject immediate reward in favor of the long-term goal. Further, functional interaction between the anteroventral prefrontal cortex and the vStr in the 'DRD' was significantly impaired in the bipolar group. These findings provide evidence for a reduced responsivity of the vStr to reward stimuli in BD, possibly related to clinical features like anhedonia. The disturbed top-down control of mesolimbic reward signals by prefrontal brain regions in BD can be interpreted in terms of a disease-related enhanced impulsivity, a trait marker of BD.

Omega-3 fatty acid deficient male rats exhibit abnormal behavioral activation in the forced swim test following chronic fluoxetine treatment: association with altered 5-HT1A and alpha2A adrenergic receptor expression

Omega-3 fatty acid deficiency during development leads to enduing alterations in central monoamine neurotransmission in rat brain. Here we investigated the effects of omega-3 fatty acid deficiency on behavioral and neurochemical responses to chronic fluoxetine (FLX) treatment. Male rats were fed diets with (CON, n = 34) or without (DEF, n = 30) the omega-3 fatty acid precursor alpha-linolenic acid (ALA) during peri-adolescent development (P21-P90). A subset of CON (n = 14) and DEF (n = 12) rats were administered FLX (10 mg/kg/d) through their drinking water for 30 d beginning on P60. The forced swimming test (FST) was initiated on P90, and regional brain mRNA markers of serotonin and noradrenaline neurotransmission were determined. Dietary ALA depletion led to significant reductions in frontal cortex docosahexaenoic acid (DHA, 22:6n-3) composition in DEF (-26%, p = 0.0001) and DEF + FLX (-32%, p = 0.0001) rats. Plasma FLX and norfluoxetine concentrations did not different between FLX-treated DEF and CON rats. During the 15-min FST pretest, DEF + FLX rats exhibited significantly greater climbing behavior compared with CON + FLX rats. During the 5-min test trial, FLX treatment reduced immobility and increased swimming in CON and DEF rats, and only DEF + FLX rats exhibited significant elevations in climbing behavior. DEF + FLX rats exhibited greater midbrain, and lower frontal cortex, 5-HT1A mRNA expression compared with all groups including CON + FLX rats. DEF + FLX rats also exhibited greater midbrain alpha2A adrenergic receptor mRNA expression which was positively correlated with climbing behavior in the FST. These preclinical data demonstrate that low omega-3 fatty acid status leads to abnormal behavioral and neurochemical responses to chronic FLX treatment in male rats.

Impulsivity in bipolar disorder: relationships with neurocognitive dysfunction and substance use history

OBJECTIVES

Impulsivity is a core feature in bipolar disorder. Although mood symptoms exacerbate impulsivity, self-reports of impulsivity are elevated, even during euthymia. Neurocognitive processes linked to impulsivity (e.g., attention, inhibition) are also impaired in patients with bipolar disorder, and a high frequency of comorbidities associated with impulsivity, such as substance use disorders, further highlights the clinical relevance of this dimension of the illness. Our objective was to assess the relationship between impulsivity and cognition in bipolar disorder.

METHODS

We evaluated impulsivity in 98 patients with bipolar disorder and its relationship with symptoms, cognition, and substance use history. We assessed self-reports of trait impulsivity [Barrett Impulsiveness Scale (BIS)] and impulsive behaviors on the Iowa Gambling Task (IGT). A comprehensive clinical and neurocognitive battery was also completed. Patients were compared with 95 healthy controls.

RESULTS

Patients with bipolar disorder had higher scores versus healthy controls on all BIS scales. Performance on the IGT was significantly impaired and patients showed a tendency toward more erratic choices. Depressive symptoms were positively correlated with trait impulsivity and with an increased tendency to attend more readily to losses versus gains on the IGT. We found no significant associations between impulsivity and neurocognition in the full bipolar sample; however, when sub-grouped based on substance abuse history, significant relationships were revealed only in subjects without a substance abuse history.

CONCLUSIONS

Our data support prior reports of increased trait impulsivity and impairment on behavioral tasks of impulsiveness in bipolar disorder and suggest a differential relationship between these illness features that is dependent upon history of substance abuse.

Hypnotizability, hypnosis and prepulse inhibition of the startle reflex in healthy women: an ERP analysis

A working model of the neurophysiology of hypnosis suggests that highly hypnotizable individuals (HHs) have more effective frontal attentional systems implementing control, monitoring performance, and inhibiting unwanted stimuli from conscious awareness, than low hypnotizable individuals (LHs). Recent studies, using prepulse inhibition (PPI) of the auditory startle reflex (ASR), suggest that HHs, in the waking condition, may show reduced sensory gating although they may selectively attend and disattend different stimuli. Using a within subject design and a strict subject selection procedure, in waking and hypnosis conditions we tested whether HHs compared to LHs showed a significantly lower inhibition of the ASR and startle-related brain activity in both time and intracerebral source localization domains. HHs, as compared to LH participants, exhibited (a) longer latency of the eyeblink startle reflex, (b) reduced N100 responses to startle stimuli, and (c) higher PPI of eyeblink startle and of the P200 and P300 waves. Hypnosis yielded smaller N100 waves to startle stimuli and greater PPI of this component than in the waking condition. sLORETA analysis revealed that, for the N100 (107 msec) elicited during startle trials, HHs had a smaller activation in the left parietal lobe (BA2/40) than LHs. Auditory pulses of pulse-with prepulse trials in HHs yielded less activity of the P300 (280 msec) wave than LHs, in the cingulate and posterior cingulate gyrus (BA23/31). The present results, on the whole, are in the opposite direction to PPI findings on hypnotizability previously reported in the literature. These results provide support to the neuropsychophysiological model that HHs have more effective sensory integration and gating (or filtering) of irrelevant stimuli than LHs.

A novel translational assay of response inhibition and impulsivity: effects of prefrontal cortex lesions, drugs used in ADHD, and serotonin 2C receptor antagonism

Animal models are making an increasing contribution to our understanding of the psychology and brain mechanisms underlying behavioral inhibition and impulsivity. The aim here was to develop, for the first time, a mouse analog of the stop-signal reaction time task with high translational validity in order to be able to exploit this species in genetic and molecular investigations of impulsive behaviors. Cohorts of mice were trained to nose-poke to presentations of visual stimuli. Control of responding was manipulated by altering the onset of an auditory 'stop-signal' during the go response. The anticipated systematic changes in action cancellation were observed as stopping was made more difficult by placing the stop-signal closer to the execution of the action. Excitotoxic lesions of medial prefrontal cortex resulted in impaired stopping, while the clinically effective drugs methylphenidate and atomoxetine enhanced stopping abilities. The specific 5-HT2C receptor antagonist SB242084 also led to enhanced response control in this task. We conclude that stop-signal reaction time task performance can be successfully modeled in mice and is sensitive to prefrontal cortex dysfunction and drug treatments in a qualitatively similar manner to humans and previous rat models. Additionally, using this model we show novel and highly discrete effects of 5-HT2C receptor antagonism that suggest manipulation of 5-HT2C receptor function may be of use in correcting maladaptive impulsive behaviors and provide further evidence for dissociable contributions of serotonergic transmission to response control.

Neural correlate of impulsivity in subjects at ultra-high risk for psychosis

OBJECTIVE

Impulsivity is one of the most commonly reported behavioral characteristics of patients with schizophrenia. Although there is accumulating evidence regarding behavioral problems in individuals at ultra-high risk (UHR) for psychosis, as yet, no study has reported on impulsivity in this population. The aim of the present study was to assess impulsivity in UHR subjects and to investigate the associated gray matter correlates.

METHOD

This study included 32 UHR subjects and 32 age- and gender-matched healthy controls (HCs). The Barratt Impulsiveness Scale version-11 (BIS-11) was employed to assess impulsivity. Differences between the groups in gray matter volume in the anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC), and orbitofrontal cortex (OFC) were assessed. Then, a correlational analysis between the BIS-11 scores and significant clusters of gray matter volume was conducted in UHR subjects.

RESULTS

UHR subjects were more impulsive than HC subjects in terms of attention (t = 3.5187, p<0.01), motor (t = 3.1751, p<0.01), and non-planning (t = 4.4154, p<0.01) scores. The gray matter volume of the ACC was negatively correlated with the motor (r = -0.472, p<0.01) and non-planning (r = -0.354, p = 0.04) scores of the BIS-11 in UHR subjects.

CONCLUSION

These results suggest that impulsivity in UHR subjects may reflect altered integrated conflict processing, which likely stems from abnormalities in the ACC, rather than altered reward/punishment processing or executive control.

Suicide attempts and psychological risk factors in patients with bipolar and unipolar affective disorder

Suicide is an important clinical problem in psychiatric patients. The highest risk of suicide attempts is noted in affective disorders. The aim of the study was looking for suicide risk factors among personality dimensions and value system in patients with diagnosis of unipolar and bipolar affective disorder (n=189 patients, n=101 controls). To establish the diagnosis, we used SCID (Structured clinical interview for diagnostic and statistical manual of mental disorders, fourth edition) questionnaire, TCI (Temperament and Character Inventory) questionnaire and Value Survey--to assess the personality. The main limitations of the study are number of participants, lack of data about stressful life events and treatment with lithium. Novelty seeking and harm avoidance dimensions constituted suicide attempt risk factors in the group of patients with affective disorders. Protective role of cooperativeness was discovered. Patients with and without suicide attempt in lifetime history varied in self-esteem position in Value Survey.

Can risk-taking be an endophenotype for bipolar disorder? A study on patients with bipolar disorder type I and their first-degree relatives

Risk-taking behavior and impulsivity are core features of bipolar disorder. Whether they are part of the inherited aspect of the illness is not clear. We aimed to evaluate risk-taking behavior as a potential endophenotype for bipolar disorders, and its relationship with impulsivity and illness features. The Balloon Analogue Risk Task (BART) and Barratt Impulsiveness Scale-11 (BIS-11) were used to assess risk-taking behavior and impulsivity respectively in 30 euthymic bipolar I patients (BD), their 25 asymptomatic first-degree relatives (BD-R), and 30 healthy controls (HC). The primary BART outcome measure was the behavioral adjustment score (number of pumps after trials where the balloon did not pop minus the number of pumps after trials where the balloon popped). BD (p < .001) and BD-R (p = .001) had similar and significantly lower adjustment scores than HC. Only BD scored significantly higher on BIS-11 total (p = .01) and motor (p = .04) subscales than HC. Neither the BART, nor impulsivity scores associated with illness features. A limitation of this study is medicated patients and a heterogeneous BD-R were included. Riskiness may be a candidate endophenotype for bipolar disorder as it appears independently from illness features, presents similarly in BD and BD-R groups and differs from impulsivity.

Is impulsivity a common trait in bipolar and unipolar disorders?

OBJECTIVES

  Impulsivity is increased in bipolar and unipolar disorders during episodes and is associated with substance abuse disorders and suicide risk. Impulsivity between episodes predisposes to relapses and poor therapeutic compliance. However, there is little information about impulsivity during euthymia in mood disorders. We sought to investigate trait impulsivity in euthymic bipolar and unipolar disorder patients, comparing them to healthy individuals and unaffected relatives of bipolar disorder patients.

METHODS

  Impulsivity was evaluated by the Barratt Impulsiveness Scale (BIS-11A) in 54 bipolar disorder patients, 25 unipolar disorder patients, 136 healthy volunteers, and 14 unaffected relatives. The BIS-11A mean scores for all four groups were compared through the Games-Howell test for all possible pairwise combinations. Additionally, we compared impulsivity in bipolar and unipolar disorder patients with and without a history of suicide attempt and substance abuse disorder.

RESULTS

  Bipolar and unipolar disorder patients scored significantly higher than the healthy controls and unaffected relatives on all measures of the BIS-11A except for attentional impulsivity. On the attentional impulsivity measures there were no differences among the unaffected relatives and the bipolar and unipolar disorder groups, but all three of these groups scored higher than the healthy participant group. There was no difference in impulsivity between bipolar and unipolar disorder subjects with and without suicide attempt. However, impulsivity was higher among bipolar and unipolar disorder subjects with past substance use disorder compared to patients without such a history.

CONCLUSIONS

  Questionnaire-measured impulsivity appears to be relatively independent of mood state in bipolar and unipolar disorder patients; it remains elevated in euthymia and is higher in individuals with past substance abuse. Elevated attentional and lower non-planning impulsivity in unaffected relatives of bipolar disorder patients distinguished them from healthy participants, suggesting that increased attentional impulsivity may predispose to development of affective disorders, while reduced attentional impulsivity may be protective.

Serotonin system gene polymorphisms are associated with impulsivity in a context dependent manner

Impulsivity is a risk factor for adverse outcomes and characterizes several psychiatric disorders and risk for suicide. There is strong evidence that genetic variation influences individual differences in impulsivity, but the details are not yet understood. There is growing interest in better understanding the context dependency of genetic effects that is reflected in studies examining gender specificity, gene×environment interaction and epistasis (gene-gene interaction). In a cross-sectional study we examined whether polymorphisms in six serotonin system candidate genes and the experience of early life trauma (age 0-12) were associated with individual differences in impulsivity in a non-clinical sample of Caucasian university students (N=424). We specifically tested potential gender specific, gene-gene, and gene×environment (early life trauma) effects. In our main analyses with Barratt Impulsiveness Scale (BIS-11) total score, there were significant (i.e. p<.01 and False Discovery Rate <.10) interactions between (1) gender and TPH2 (rs1386483) genotype; (2) gender and HTR2A (rs6313) genotype; and epistatic interactions among (3) 5-HTTLPR and MAOA uVNTR; (4) 5-HTTLPR and rs6313 and (5) HTR1B (rs6296) and rs6313 genotypes. Our results strongly support the explicit investigation of context dependent genetic effects on impulsivity and may help to resolve some of the conflicting reports in the literature.

Trait impulsivity as an endophenotype for bipolar I disorder

OBJECTIVE

Impulsivity, conceptualized as impairment in planning and poor attentional and inhibitory control, is a key feature of bipolar disorder. Familial risk for bipolar disorder is known to affect inhibitory control but its impact on the attentional and planning dimensions of impulsivity is still unclear.

METHODS

We administered the Barratt Impulsiveness Scale, version 11 (BIS-11) to 54 euthymic individuals with DSM-IV bipolar I disorder, 57 of their clinically unaffected siblings, and 49 healthy comparison subjects. Groups were compared on the attentional (rapid shifts in attention/impatience with complexity), motor (acting impetuously), and non-planning (absence of weighing upon long-term consequences of actions) subscales of the BIS-11, and on total BIS-11 score. To investigate functional implications of trait impulsivity, total BIS-11 score was examined in relation to current psychosocial functioning and criminal history.

RESULTS

Individuals with bipolar I disorder had elevated scores compared to healthy comparison subjects on BIS-11 total score and all three subscales (p < 0.0001). Unaffected siblings had elevated BIS-11 total score (p = 0.0037), motor (p = 0.0027), and non-planning (p = 0.0379) subscales in comparison to unrelated healthy controls. Total BIS-11 score was negatively associated with global assessment of functioning (GAF) score (β = -0.32, p < 0.0001).

CONCLUSIONS

 Our results suggest that impulsivity is sensitive to familial liability for the illness, making it a potential endophenotype for bipolar disorder.

Chronic corticosterone exposure during adolescence reduces impulsive action but increases impulsive choice and sensitivity to yohimbine in male Sprague-Dawley rats

Chronic stress during adolescence is associated with an increased risk for alcoholism and addictive disorders. Addiction is also associated with increased impulsivity, and stress during adolescence could alter cortical circuits responsible for response inhibition. Therefore, the present study determined the effect of chronic exposure to the stress hormone corticosterone (CORT) during adolescence on tests of impulsivity in adulthood and examined possible biochemical mechanisms. Male Sprague-Dawley rats were exposed to CORT by their drinking water during adolescence (post-natal day 30-50). The rats were then tested in adulthood to assess behavior on the 5-choice serial reaction time task (5CSRTT), stop-signal reaction time task (SSRTT), and the delay-discounting task, which differentially assess attention, impulsive action, and impulsive choice. Yohimbine-induced impulsivity on the 5CSRTT and biochemical analysis of the lateral orbital frontal cortex (lOFC) was also assessed owing to the ability of yohimbine to activate the hypothalamic-pituitary-adrenal axis and influence impulsivity. Adolescent CORT-treated rats were found to behave largely like controls on the 5CSRTT, but did show reduced premature responses when the intertrial interval was increased. Nevertheless, the CORT-treated rats tended to have more yohimbine-induced impulsive responses at low doses on this task, which was not found to be due to increased pCREB in the lOFC, but could be related to a higher expression/activity of the AMPA receptor subunit GluR1. Adolescent CORT-treated rats performed more accurately on the SSRTT, but showed greater impulsivity on the delay-discounting task, as indicated by steeper discounting functions. Therefore, adolescent CORT exposure reduced impulsive action but increased impulsive choice, indicating that chronic stress hormone exposure in adolescence can have long-term consequences on behavior.

Different measures of impulsivity in patients with anxiety disorders: a case control study

The relationship between anxiety and impulsivity is controversial and not well explored. The present investigation aims to compare impulsivity, measured by different rating tools, in patients with anxiety disorders vs. healthy controls. Forty-seven subjects with different anxiety disorders and 45 matched controls underwent diagnostic and symptomatological evaluations by the Mini Neuropsychiatric Interview (M.I.N.I) Plus 5.0, Bech-Raphaelsen Depression and Mania Scale (BRDMS), State-Trait Anxiety Inventory (STAI), Hypomania Check List (HCL-32) and the Clinical Global Impression (CGI); temperamental evaluations by the Questionnaire for the Affective and Anxious Temperament Evaluation of Memphis, Pisa, Paris and San Diego-Modified (TEMPS-M), the Separation Anxiety Sensitivity Index (SASI), the Interpersonal Sensitivity Symptoms Inventory (ISSI); and psychometric and a neurocognitive evaluations of impulsivity using the Barratt Impulsiveness Scale (BIS-11) and the Immediate and Delayed Memory Task (IMT-DMT). Subjects with anxiety disorders were more impulsive than the controls in all the explored measures, with higher scores in symptomatological and, temperamental scales. Patients with anxiety disorders but without a lifetime history of comorbid major mood episodes had greater trait and state impulsivity than controls. Further investigations are needed to assess the extent to which impulsivity might or might not be directly related to the anxiety disorder.

Does anxiety increase impulsivity in patients with bipolar disorder or major depressive disorder?

The objective of this study was to examine whether anxiety increases impulsivity among patients with bipolar disorder (BPD) and major depressive disorder (MDD). Subjects comprised 205 BPD (mean age ± SD 36.6 ± 11.5 y; 29.3% males) and 105 with MDD (mean age ± SD 38 ± 13.1 y; 29.5% males) diagnosed using the DSM-IV-SCID. Impulsivity was assessed with the Barratt Impulsivity Scale and anxiety with the Hamilton Anxiety Rating Scale. Comorbid anxiety disorders were present in 58.9% of the BPD and 29.1% of MDD. BPD were significantly more impulsive than MDD (p < 0.001), and both BPD and MDD subjects showed significantly higher impulsivity when anxiety was present either as a comorbidity (p = 0.010) or as a symptom (p = 0.011). Impulsivity rose more rapidly with increasing anxiety symptoms in MDD than in BPD. The presence of anxiety, either as a comorbid disorder or as current anxiety symptoms, is associated with higher impulsivity in subjects with either BPD or MDD.

Relationship between suicidality and impulsivity in bipolar I disorder: a diffusion tensor imaging study

BACKGROUND

Impulsivity is characteristic of individuals with bipolar disorder and may be a contributing factor to the high rate of suicide in patients with this disorder. Although white matter abnormalities have been implicated in the pathophysiology of bipolar disorder, their relationship to impulsivity and suicidality in this disorder has not been well-investigated.

METHODS

Diffusion tensor imaging scans were acquired in 14 bipolar disorder patients with a prior suicide attempt, 15 bipolar disorder patients with no prior suicide attempt, and 15 healthy volunteers. Bipolar disorder patients received clinical assessments including measures of impulsivity, depression, mania, and anxiety. Images were processed using the Tract-Based Spatial Statistics method in the FSL software package.

RESULTS

Bipolar disorder patients with a prior suicide attempt had lower fractional anisotropy (FA) within the left orbital frontal white matter (p < 0.05, corrected) and higher overall impulsivity compared to patients without a previous suicide attempt. Among patients with a prior suicide attempt, FA in the orbital frontal white matter region correlated inversely with motor impulsivity.

CONCLUSIONS

Abnormal orbital frontal white matter may play a role in impulsive and suicidal behavior among patients with bipolar disorder.

Striatal and cortical midline activation and connectivity associated with suicidal ideation and depression in bipolar II disorder

BACKGROUND

Considerable evidence implicates dysfunction of striatal and cortical midline structure (CMS) circuitry in mood disorders. Whether such aberrations exist in bipolar II depression is unknown.

METHODS

Sixteen unmedicated subjects with bipolar II depression and 19 healthy controls were studied using functional MRI and a motor activation paradigm. Analyses of both activation and functional connectivity were conducted.

RESULTS

A history of suicidal ideation (SI) was negatively correlated with activation of the left putamen while depression severity was positively correlated with activation of the left thalamus. The superior bilateral putamen was simultaneously correlated with depression severity and anti-correlated with SI. Striatal functional connectivity was altered with the bilateral CMS and right inferior parietal lobule. Depression severity was correlated with strength of connectivity between the bilateral striatum and the right lingual gyrus and left cerebellum.

LIMITATIONS

Only males experiencing an episode of major depression were studied.

CONCLUSIONS

Striatal and CMS circuit abnormalities likely contribute to the neurobiology of bipolar II depression. Altered connectivity of the striatum may directly impact depression severity. Further, dissociable components of activation associated with depression severity and suicidal ideation may exist. Finally, the motor activation paradigm used in this study appears to be a useful probe of some neural processes underlying bipolar II depression.