Dysthymia and depressive disorders: dopamine hypothesis

Atypical antipsychotic drugs in dysthymia: placebo controlled studies of amisulpride versus imipramine, versus amineptine

In order to assess the therapeutic efficacy of amisulpride in dysthymic disorder, two randomised double-blind trials were conducted in France. Both studies included outpatients meeting DSM-III-R criteria for primary dysthymia. Cases of double depressed patients with a mild or moderate major depressive episode superimposed to dysthymia were also eligible. The first study of a three-month duration compared amineptine (200 mg/day) to amisulpride (50 mg/day) and placebo. The second study of a six-month duration compared the therapeutic effects of imipramine (100 mg/day) to amisulpride (50 mg/day) and placebo. Results of the intention to treat analysis and of the end-point analysis were compelling and very similar: significant differences were demonstrated for all primary criteria between amisulpride and placebo and between imipramine and placebo but not between amisulpride and imipramine. For both primary criteria and the responder rate (CGI), statistically significant differences were evidenced between amisulpride and placebo and amineptine and placebo. The same differences were evidenced for SANS subscores. Beneficial effects of low doses of amisulpride in chronic depressive condition can therefore be discussed.

Conditioned task-set competition: Neural mechanisms of emotional interference in depression

Depression has been associated with increased response times at the incongruent-, neutral-, and negative-word trials of the classical and emotional Stroop tasks (Epp et al., Clinical Psychology Review, 32, 316-328, 2012). Response-time slowdown effects at incongruent- and negative-word trials of the Stroop tasks were reported to correlate with depressive severity, indicating strong relevance of the effects to the symptomatology. This study proposes a novel integrative computational model of neural mechanisms of both the classical and emotional Stroop effects, drawing on the previous prominent theoretical explanations of performance at the classical Stroop task (Cohen, Dunbar, & McClelland, Psychological Review, 97, 332-361, 1990; Herd, Banich, & O'Reilly, Journal of Cognitive Neuroscience, 18, 22-32, 2006), and in addition suggesting that negative emotional words represent conditioned stimuli for future negative outcomes. The model is shown to explain the classical Stroop effect and the slow (between-trial) emotional Stroop effect with biologically plausible mechanisms, providing an advantage over the previous theoretical accounts (Matthews & Harley, Cognition & Emotion, 10, 561-600, 1996; Wyble, Sharma, & Bowman, Cognition & Emotion, 22, 1019-1051, 2008). Simulation results suggested a candidate mechanism responsible for the pattern of depressive performance at the classical and the emotional Stroop tasks. Hyperactivity of the amygdala, together with increased inhibitory influence of the amygdala over dopaminergic neurotransmission, could be at the origin of the performance deficits.

A comparison of paroxetine versus paroxetine plus amisulpride in the treatment of dysthymic disorder: efficacy and psychosocial outcomes

Dysthymic disorder is a chronic depressive condition with considerable psychosocial impairment. Even if DD patients respond to various antidepressant medications, there has been little systematic study on antidepressant-refractory DD. Only a few trials have evaluated the effects of treatment on psychosocial functioning of dysthymic patients. In this 3-month, open-label study, 60 outpatients with DSM-IV criteria for dysthymic disorder who failed to respond to 3-month treatment with paroxetine 20 mg/day were randomly assigned to treatment with paroxetine 40 mg/day or paroxetine 20 mg/day plus amisulpride 50 mg/day. The effects of the two treatments were assessed for both mood symptoms (21-item Hamilton Rating Scale for Depression, Montgomery-Asberg Depression Rating Scale, Clinical Global Impression, severity and improvement) and psychosocial outcomes (DSM-IV Global Assessment of Functioning, Social Adaptation Self-evaluation Scale). Analysis of variance on all rating scales showed that both treatments were effective over this observation period. Response and remission rates did not differ in the treatment groups. A significantly greater psychosocial improvement was observed in the group receiving combined treatment compared with patients receiving paroxetine alone. Both treatments appeared to be effective in our sample of dysthymic subjects. Combined treatment with paroxetine and amisulpride resulted in a better outcome in terms of social functioning.

Extrapyramidal symptoms and antidepressant drugs: neuropharmacological aspects of a frequent interaction in the elderly

Depression is the most prevalent functional psychiatric disorder in late life. The problem of motor disorders associated with antidepressant use is relevant in the elderly. Elderly people are physically more frail and more likely to be suffering from physical illness, and any drug given may exacerbate pre-existing diseases, or interact with other drug treatments being administered for physical conditions. Antidepressants have been reported to induce extrapyramidal symptoms, including parkinsonism. These observations prompted us to review the neurobiological mechanism that may be involved in this complex interplay including neurotransmitters and neuronal circuits involved in movement and emotion control and their changes related to aging and disease. The study of the correlations between motor and mood disorders and their putative biochemical bases, as presented in this review, provide a rationale either to understand or to foresee motor side effects for psychotropic drugs, in particular antidepressants.

Dopaminergic sensitivity and prediction of antidepressant response

This study was designed to examine neuroendocrine predictors of antidepressant response to the selective serotonin reuptake inhibitor (SSRI) paroxetine. We assessed the prognostic utility of the apomorphine stimulation test by examining the relationship between pretreatment change in growth hormone (GH) following apomorphine and acute response to paroxetine treatment. We hypothesized that those subjects with most marked pretreatment dopaminergic supersensitivity, as manifested by greatest change in GH, would be most likely to show an early antidepressant response and would also be more likely to develop manic or hypomanic symptoms on paroxetine. Contrary to our hypothesis, greater dopamine postsynaptic sensitivity was associated with greater resistance to paroxetine treatment. In our sample of 13 subjects with a major depressive episode, pretreatment GH response to apomorphine per unit weight was inversely correlated with change in Hamilton depression rating scale following 6 weeks of paroxetine. Within the group of subjects who showed mood elevation on paroxetine, there was a trend towards greater GH response being associated with slower antidepressant response. With regard to the development of manic or hypomanic symptoms on paroxetine, change in GH per unit weight not did distinguish the two subjects who subsequently developed paroxetine-induced hypomania from other subjects. The seven subjects with previous antidepressant-induced hypomania did not differ from the other subjects in change in GH response per unit weight. The finding that subjects who had low dopamine receptor responsivity pretreatment were more likely to have an antidepressant response with paroxetine is consistent with recent suggestions that the therapeutic effect of SSRIs may be mediated through increased dopamine receptor sensitivity in the mesolimbic system. Further work assessing pretreatment and post-treatment GH response to apomorphine will help to test the hypothesis that low dopamine receptor responsivity predicts antidepressant response to SSRIs.

Amisulpride in medium-term treatment of dysthymia: a six-month, double-blind safety study versus amitriptyline. AMILONG investigators

Two hundred and fifty patients participated in a 6-month, double-blind study to evaluate safety and efficacy of a medium-term treatment with amisulpride 50 mg/day versus amitriptyline 25-75 mg/day in dysthymia. Patients in treatment groups (165 amisulpride; 85 amitriptyline) were well balanced for demographic and baseline characteristics. A total of 139 patients (93 amisulpride, 46 amitriptyline) completed the study with no statistically significant differences in reasons for premature termination between the two groups. A tendency towards a higher incidence of treatment-emergent adverse events with amitriptyline was observed (73% versus 64% amisulpride). In the amitriptyline group, a statistically significantly higher incidence of central nervous system (41% versus 24%, p=0.004) and autonomic nervous system disorders (45% versus 16%, p < 0.0001) was reported. Conversely, endocrine disorders were more frequent with amisulpride (18% versus 7%, p=0.023). Efficacy was a secondary end-point. Results of the symptom rating scales indicate that both drugs were equally effective: 60% and 62% of patients under amisulpride and amitriptyline, respectively, achieved a reduction > or = 50% of the Montgomery and Asberg Rating Scale total score at end-point. On the item 'global improvement' of the Clinical Global Impression, 67% of amisulpride and 68% of amitriptyline patients were rated as 'very much' or 'much' improved. Results of the present study in a large patient population further confirm the safe use of amisulpride in dysthymia and support its administration upon a medium-term treatment period.

Dysthymia: clinical picture, extent of overlap with chronic fatigue syndrome, neuropharmacological considerations, and new therapeutic vistas

Dysthymia, as defined in the American Psychiatric Association and International Classification of Mental Disorders, refers to a prevalent form of subthreshold depressive pathology with gloominess, anhedonia, low drive and energy, low self-esteem and pessimistic outlook. Although comorbidity with panic, social phobic, and alcohol use disorders has been described, the most significant association is with major depressive episodes. Family history is loaded with affective, including bipolar, disorders. The latter finding explains why dysthymia, especially when onset is in childhood, can lead to hypomanic switches, both spontaneously and upon pharmacologic challenge in as many as 30%. Indeed, antidepressants from different classes -tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs), reversible inhibitors of monoamine oxidase A (RIMAs), selective serotonin-reuptake inhibitors (SSRIs) and, more recently, amisulpride, and spanning noradrenergic, serotonergic as well as dopaminergic mechanisms of action - have been shown to be effective against dysthymia in an average of 65% of cases. This is a promising development because social and characterologic disturbances so pervasive in dysthymia often, though not always, recede with continued pharmacotherapy beyond acute treatment. Despite symptomatic overlap of dysthymia with chronic fatigue syndrome - especially with respect to the cluster of symptoms consisting of low drive, lethargy, lassitude and poor concentration - neither the psychopathologic status, nor the pharmacologic response profile of the latter syndrome is presently understood. Chronic fatigue today is where dysthymia was two decades ago. We submit that the basic science - clinical paradigm that has proven so successful in dysthymia could, before too long, crack down the conundrum of chronic fatigue as well. At a more practical level, we raise the possibility that a subgroup within the chronic fatigue group represents a variant of dysthymia.