Effective Altruism as an Ethical Lens on Research Priorities

Effective altruism is an ethical framework for identifying the greatest potential benefits from investments. Here, we apply effective altruism concepts to maximize research benefits through identification of priority stakeholders, pathosystems, and research questions and technologies. Priority stakeholders for research benefits may include smallholder farmers who have not yet attained the minimal standards set out by the United Nations Sustainable Development Goals; these farmers would often have the most to gain from better crop disease management, if their management problems are tractable. In wildlands, prioritization has been based on the risk of extirpating keystone species, protecting ecosystem services, and preserving wild resources of importance to vulnerable people. Pathosystems may be prioritized based on yield and quality loss, and also factors such as whether other researchers would be unlikely to replace the research efforts if efforts were withdrawn, such as in the case of orphan crops and orphan pathosystems. Research products that help build sustainable and resilient systems can be particularly beneficial. The "value of information" from research can be evaluated in epidemic networks and landscapes, to identify priority locations for both benefits to individuals and to constrain regional epidemics. As decision-making becomes more consolidated and more networked in digital agricultural systems, the range of ethical considerations expands. Low-likelihood but high-damage scenarios such as generalist doomsday pathogens may be research priorities because of the extreme potential cost. Regional microbiomes constitute a commons, and avoiding the "tragedy of the microbiome commons" may depend on shifting research products from "common pool goods" to "public goods" or other categories. We provide suggestions for how individual researchers and funders may make altruism-driven research more effective.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Problem behaviours and symptom dimensions of psychiatric disorders in adults with intellectual disabilities: An exploratory and confirmatory factor analysis

BACKGROUND

The limited evidence on the relationship between problem behaviours and symptoms of psychiatric disorders experienced by adults with intellectual disabilities leads to conflict about diagnostic criteria and confused treatment. This study examined the relationship between problem behaviours and other psychopathology, and compared the predictive validity of dimensional and categorical models experienced by adults with intellectual disabilities.

METHODS

Exploratory and confirmatory factor analyses appropriate for non-continuous data were used to derive, and validate, symptom dimensions using two clinical datasets (n=457; n=274). Categorical diagnoses were derived using DC-LD. Severity and 5-year longitudinal outcome was measured using a battery of instruments.

RESULTS

Five factors/dimensions were identified and confirmed. Problem behaviours were included in an emotion dysregulation-problem behaviour dimension that was distinct from the depressive, anxiety, organic and psychosis dimensions. The dimensional model had better predictive validity than categorical diagnosis.

CONCLUSIONS

International classification systems should not include problem behaviours as behavioural equivalents in diagnostic criteria for depression or other psychiatric disorders. Investigating the relevance of emotional regulation to psychopathology may provide an important pathway for development of improved interventions.

WHAT THIS PAPER ADDS

There is uncertainty whether new onset problem behaviours or a change in longstanding problem behaviours should be considered as symptoms of depression or other types of psychiatric disorders in adults with intellectual disabilities. The validity of previous studies was limited by the use of pre-defined, categorical diagnoses or unreliable statistical methods. This study used robust statistical modelling to examine problem behaviours within a dimensional model of symptoms. We found that problem behaviours were included in an emotional dysregulation dimension and not in the dimension that included symptoms that are typical of depression. The dimensional model of symptoms had greater predictive validity than categorical diagnoses of psychiatric disorders. Our findings suggest that problem behaviours are a final common pathway for emotional distress in adults with intellectual disabilities so clinicians should not use a change in problem behaviours as a diagnostic criterion for depression, or other psychiatric disorders.

Statistical modelling studies examining the dimensional structure of psychopathology experienced by adults with intellectual disabilities: Systematic review

Diagnosing mental ill-health using categorical classification systems has limited validity for clinical practice and research. Dimensions of psychopathology have greater validity than categorical diagnoses in the general population, but dimensional models have not had a significant impact on our understanding of mental ill-health and problem behaviours experienced by adults with intellectual disabilities. This paper systematically reviews the methods and findings from intellectual disabilities studies that use statistical methods to identify dimensions of psychopathology from data collected using structured assessments of psychopathology. The PRISMA framework for systematic review was used to identify studies for inclusion. Study methods were compared to best-practice guidelines on the use of exploratory factor analysis. Data from the 20 studies included suggest that it is possible to use statistical methods to model dimensions of psychopathology experienced by adults with intellectual disabilities. However, none of the studies used methods recommended for the analysis of non-continuous psychopathology data and all 20 studies used statistical methods that produce unstable results that lack reliability. Statistical modelling is a promising methodology to improve our understanding of mental ill-health experienced by adults with intellectual disabilities but future studies should use robust statistical methods to build on the existing evidence base.

Targeting ultrasound remission in early rheumatoid arthritis: the results of the TaSER study, a randomised clinical trial

Objective

To investigate whether an intensive early rheumatoid arthritis (RA) treat-to-target (T2T) strategy could be improved through the use of musculoskeletal ultrasound (MSUS) assessment of disease activity.

Methods

111 newly diagnosed patients with RA or undifferentiated arthritis (symptom duration <1 year) were randomised to strategies that aimed to attain either DAS28-erythrocyte sedimentation rate (ESR)<3.2 (control) or a total power Doppler joint count≤1 during a combined DAS28-ESR/MSUS assessment (intervention). MSUS examination was indicated if: DAS28-ESR<3.2 or DAS28-ESR≥3.2 with two swollen joints. Step-up disease-modifying antirheumatic drug (DMARD) escalation was standardised: methotrexate monotherapy, triple therapy and then etanercept/triple therapy. American College of Rheumatology (ACR) core-set variables were assessed 3 monthly by a metrologist blinded to group allocation. MRI of dominant hand and wrist, and plain radiographs of hands and feet were undertaken at baseline and 18 months for grading by two readers using the Outcome Measures in Rheumatology (OMERACT) Rheumatoid Arthritis MRI Scoring System (RAMRIS) and van der Heijde/Sharp Score, respectively. The coprimary outcomes were mean change from baseline of DAS44 and RAMRIS erosion score.

Results

Groups were matched for baseline clinical, demographic and radiographic features. The intervention group received more intensive DMARD therapy. Both groups demonstrated significant improvements in DAS44 (mean change: control −2.58, intervention −2.69; 95% CI difference between groups −0.70 to 0.48; p=0.72). There were no significant between-group differences for any ACR core-set variables, except DAS44 remission after 18 months (control 43%, intervention 66%; p=0.03). There was minimal progression of MRI and radiographic erosions and no difference in imaging outcomes or serious adverse event rates.

Conclusions

In early RA, a MSUS-driven T2T strategy led to more intensive treatment, but was not associated with significantly better clinical or imaging outcomes than a DAS28-driven strategy.

Trial registration number

NCT00920478.

The effects of anti-depressants on depression symptom scores at 12 months follow-up in patients with cardiometabolic disease: Results from a large primary care cohort

Background:

Evidence on the long-term usefulness of anti-depressants in managing depression in cardiometabolic disease is limited.

Aim:

We examined the effects of anti-depressant prescribing on depressive symptoms at 12 months follow-up in patients with cardiometabolic disease and a positive depression screening result at baseline.

Design and Setting:

We retrospectively reviewed routine UK primary care data for patients with coronary heart disease, diabetes and previous stroke for the year 2008–2009. 35,537 patients with one of the three above diseases underwent depression screening using the Hospital Anxiety and Depression Scale (HADS-D). Of 7080 patients with a positive screening result (HADS-D ≥ 8), 3933 (55.5%) patients had a repeat HADS-D recorded at 12 months follow-up.

Methods:

We compared the change in HADS-D at follow-up and remission rate in those who were prescribed anti-depressants (n = 223) against those who were not (n = 3710).

Results:

The mean change in HADS-D from baseline, for the nonprescribed group was similar to the reduction observed in patients who were continuously prescribed (n = 93) with anti-depressants during follow-up. Patients who were prescribed intermittently (n = 72) or only one (n = 58) prescription during follow-up had a lower reduction in HADS-D compared to the nonprescribed group. There was no difference in remission rates between continuously prescribed and the nonprescribed group, but remission was lower in patients prescribed intermittently and single prescription.

Conclusion:

Improvement in depressive symptoms in patients with cardiometabolic disease at 12 months was not any better in patients prescribed with anti-depressants compared to the nonprescribed group. The role of anti-depressants in the management of depression in cardiometabolic disease merits further investigation.

An investigation of two-dimensional ultrasound carotid plaque presence and intima media thickness in middle-aged South Asian and European men living in the United kingdom

Objectives

Ultrasound studies of carotid intima media thickness (cIMT) and plaques are limited in South Asians, a group at elevated cardiovascular disease (CVD) risk. We determined whether South Asians have a difference in these ultrasound markers compared to Europeans living in the United Kingdom and whether measured risk factor(s) could account for any such differences.

Methods

One hundred South Asian men, aged 40 to 70 years and 100 European men of similar age and BMI, without diagnosed CVD or diabetes, underwent carotid ultrasound for measurement of cIMT and carotid plaque presence. Physical activity, cardiorespiratory fitness, anthropometry and blood pressure were assessed, fasted blood taken for measurement of cardiometabolic risk factors and demographic and lifestyle factors recorded.

Results

Age-adjusted mean (SD) cIMT was similar in South Asians and Europeans (0.64 (0.16) mm v 0.65 (0.12) mm, p = 0.64). Plaque was present in 48 South Asians and 37 Europeans and overall, there was no age-adjusted difference between South Asian and Europeans for plaque score(odds ratio 1.49, 95% CI, 0.86-2.80, p = 0.16), however, South Asians appeared to have more plaques at a younger age than Europeans; at age 40-50 years the odds of South Asians having plaques was 2.63 (95% CI, 1.16-5.93) times that for Europeans.

Conclusions

cIMT is similar between healthy South Asian and European men. Whilst there was no overall difference in plaque presence in South Asians, there is an indication of greater plaque prevalence at younger ages - an observation requiring further investigation. Prospective studies linking plaques to CVD outcomes in South Asians are needed to investigate whether these measures help improve CVD risk prediction.

Financial incentives for smoking cessation in pregnancy: randomised controlled trial

OBJECTIVE

To assess the efficacy of a financial incentive added to routine specialist pregnancy stop smoking services versus routine care to help pregnant smokers quit.

DESIGN

Phase II therapeutic exploratory single centre, individually randomised controlled parallel group superiority trial.

SETTING

One large health board area with a materially deprived, inner city population in the west of Scotland, United Kingdom.

PARTICIPANTS

612 self reported pregnant smokers in NHS Greater Glasgow and Clyde who were English speaking, at least 16 years of age, less than 24 weeks pregnant, and had an exhaled carbon monoxide breath test result of 7 ppm or more. 306 women were randomised to incentives and 306 to control.

INTERVENTIONS

The control group received routine care, which was the offer of a face to face appointment to discuss smoking and cessation and, for those who attended and set a quit date, the offer of free nicotine replacement therapy for 10 weeks provided by pharmacy services, and four, weekly support phone calls. The intervention group received routine care plus the offer of up to £400 of shopping vouchers: £50 for attending a face to face appointment and setting a quit date; then another £50 if at four weeks' post-quit date exhaled carbon monoxide confirmed quitting; a further £100 was provided for continued validated abstinence of exhaled carbon monoxide after 12 weeks; a final £200 voucher was provided for validated abstinence of exhaled carbon monoxide at 34-38 weeks' gestation.

MAIN OUTCOME MEASURE

The primary outcome was cotinine verified cessation at 34-38 weeks' gestation through saliva (<14.2 ng/mL) or urine (<44.7 ng/mL). Secondary outcomes included birth weight, engagement, and self reported quit at four weeks.

RESULTS

Recruitment was extended from 12 to 15 months to achieve the target sample size. Follow-up continued until September 2013. Of the 306 women randomised, three controls opted out soon after enrolment; these women did not want their data to be used, leaving 306 intervention and 303 control group participants in the intention to treat analysis. No harms of financial incentives were documented. Significantly more smokers in the incentives group than control group stopped smoking: 69 (22.5%) versus 26 (8.6%). The relative risk of not smoking at the end of pregnancy was 2.63 (95% confidence interval 1.73 to 4.01) P<0.001. The absolute risk difference was 14.0% (95% confidence interval 8.2% to 19.7%). The number needed to treat (where financial incentives need to be offered to achieve one extra quitter in late pregnancy) was 7.2 (95% confidence interval 5.1 to 12.2). The mean birth weight was 3140 g (SD 600 g) in the incentives group and 3120 (SD 590) g in the control group (P=0.67).

CONCLUSION

This phase II randomised controlled trial provides substantial evidence for the efficacy of incentives for smoking cessation in pregnancy; as this was only a single centre trial, incentives should now be tested in different types of pregnancy cessation services and in different parts of the United Kingdom.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN87508788.

Predictors of positive and negative parenting behaviours: evidence from the ALSPAC cohort

Background

This study aimed to establish the predictors of positive and negative parenting behaviours in a United Kingdom population. The majority of previous research has focused on specific risk factors and has used a variety of outcome measures. This study used a single assessment of parenting behaviours and started with a wide range of potential pre- and post-natal variables; such an approach might be used to identify families who might benefit from parenting interventions.

Methods

Using a case-control subsample of 160 subjects from the Avon Longitudinal Study of Parents and Children (ALSPAC), regression analysis was undertaken to model parenting behaviours at 12 months as measured by the Mellow Parenting Observational System.

Results

Positive parenting increased with maternal age at delivery, levels of education and with prenatal anxiety. More negative interactions were observed among younger mothers, mothers with male infants, with prenatal non-smokers and among mothers who perceived they had a poor support structure.

Conclusions

This study indicates two factors which may be important in identifying families most at risk of negative parenting: younger maternal age at delivery and lack of social support during pregnancy. Such factors could be taken into account when planning provision of services such as parenting interventions. We also established that male children were significantly more likely to be negatively parented, a novel finding which may suggest an area for future research. However the findings have to be accepted cautiously and have to be replicated, as the measures used do not have established psychometric validity and reliability data.

Association between parent-infant interactions in infancy and disruptive behaviour disorders at age seven: a nested, case-control ALSPAC study

BACKGROUND

Effective early intervention to prevent oppositional/conduct disorders requires early identification of children at risk. Patterns of parent-child interaction may predict oppositional/conduct disorders but large community-based prospective studies are needed to evaluate this possibility.

METHODS

We sought to examine whether the Mellow Parenting Observational System (MPOS) used to assess parent-infant interactions at one year was associated with psychopathology at age 7. The MPOS assesses positive and negative interactions between parent and child. It examines six dimensions: anticipation of child's needs, responsiveness, autonomy, cooperation, containment of child distress, and control/conflict; these are summed to produce measures of total positive and negative interactions. We examined videos from the Avon Longitudinal Study of Parents and Children (ALSPAC) sub-cohort who attended the 'Children in Focus' clinic at one year of age. Our sample comprised 180 videos of parent-infant interaction: 60 from infants who received a psychiatric diagnostic categorisation at seven years and 120 randomly selected controls who were group-matched on sex.

RESULTS

A negative association between positive interactions and oppositional/conduct disorders was found. With the exception of pervasive developmental disorders (autism), an increase of one positive interaction per minute predicted a 15% (95% CI: 4% to 26%) reduction in the odds of the infant being case diagnosed. There was no statistically significant relationship between negative parenting interactions and oppositional/conduct disorders, although negative interactions were rarely observed in this setting.

CONCLUSIONS

The Mellow Parenting Observation System, specifically low scores for positive parenting interactions (such as Responsiveness which encompasses parental warmth towards the infant), predicted later psychiatric diagnostic categorisation of oppositional/conduct disorders.

Tightening up? Impact of musculoskeletal ultrasound disease activity assessment on early rheumatoid arthritis patients treated using a treat to target strategy

OBJECTIVE

To determine the level of agreement and potential impact on disease-modifying antirheumatic drug (DMARD) escalation decisions and of adding musculoskeletal ultrasound (MSUS) assessment of disease activity to the Disease Activity Score in 28 joints (DAS28) in early rheumatoid arthritis (RA).

METHODS

Data were gathered from 53 early RA patients randomized to the MSUS assessment group of the Targeting Synovitis in Early Rheumatoid Arthritis study. DAS28 scores were calculated every month. MSUS was performed on patients with low disease activity (DAS28 <3.2) and on those with moderate disease activity (3.2 ≤ DAS28 <5.1) without clinically swollen joints (swollen joint count [SJC] ≤1). Fourteen joints (bilateral proximal interphalangeal joints 2 and 3, metacarpophalangeal [MCP] joints 2 and 3, the radiocarpal, and metatarsophalangeal joints 2 and 5) were examined. Active disease was defined as ≥2 joints demonstrating any power Doppler (PD) signal. Data from 414 paired DAS28 and MSUS assessments were pooled to determine the level of agreement between each method.

RESULTS

A total of 369 MSUS assessments were conducted on patients with DAS28 <3.2; 92 (25%) of these assessments identified active disease. A total of 271 MSUS assessments were performed on those with DAS28 <2.6; 66 (24%) of these identified active disease. Forty-five MSUS assessments were conducted on patients with 3.2 ≤ DAS28 <5.1 and SJC ≤1; 15 (33%) of these assessments confirmed active disease. On 120 occasions (29%), MSUS findings contradicted the DAS28 and led to modified treatment decisions. The joints that most frequently exhibited PD signal were radiocarpal and index and middle MCP joints.

CONCLUSION

Compared to the DAS28, global RA disease activity assessment using a limited MSUS joint set provided additional disease activity information and led to altered treatment decisions in a significant minority of occasions. This may allow further tailoring of DMARD therapy by supporting DMARD escalation in patients with continuing subclinical synovitis and preventing escalation in symptomatic patients with minimal clinical and/or ultrasonographic synovitis.

Lower cardiorespiratory fitness contributes to increased insulin resistance and fasting glycaemia in middle-aged South Asian compared with European men living in the UK

AIMS/HYPOTHESIS

This study aimed to determine the extent to which increased insulin resistance and fasting glycaemia in South Asian men, compared with white European men, living in the UK, was due to lower cardiorespiratory fitness (maximal oxygen uptake [VO(2max)]) and physical activity.

METHODS

One hundred South Asian and 100 age- and BMI-matched European men without diagnosed diabetes, aged 40-70 years, had fasted blood taken for measurement of glucose concentration, HOMA-estimated insulin resistance (HOMA(IR)), plus other risk factors, and underwent assessment of physical activity (using accelerometry), VO(2max), body size and composition, and demographic and other lifestyle factors. For 13 South Asian and one European man, HbA1c levels were >6.5% (>48 mmol/mol), indicating potential undiagnosed diabetes; these men were excluded from the analyses. Linear regression models were used to determine the extent to which body size and composition, fitness and physical activity variables explained differences in HOMA(IR) and fasting glucose between South Asian and European men.

RESULTS

HOMA(IR) and fasting glucose were 67% (p < 0.001) and 3% (p < 0.018) higher, respectively, in South Asians than Europeans. Lower VO(2max), lower physical activity and greater total adiposity in South Asians individually explained 68% (95% CI 45%, 91%), 29% (11%, 46%) and 52% (30%, 80%), respectively, and together explained 83% (50%, 119%) (all p < 0.001) of the ethnic difference in HOMA(IR). Lower VO(2max) and greater total adiposity, respectively, explained 61% (9%, 111%) and 39% (9%, 76%) (combined effect 63% [8%, 115%]; all p < 0.05) of the ethnic difference in fasting glucose.

CONCLUSIONS/INTERPRETATION

Lower cardiorespiratory fitness is a key factor associated with the excess insulin resistance and fasting glycaemia in middle-aged South Asian, compared with European, men living in the UK.

Challenges and implications of routine depression screening for depression in chronic disease and multimorbidity: a cross sectional study

Background

Depression screening in chronic disease is advocated but its impact on routine practice is uncertain. We examine the effects of a programme of incentivised depression screening in chronic disease within a UK primary care setting.

Methods and Findings

Cross sectional analysis of anonymised, routinely collected data (2008-9) from family practices in Scotland serving a population of circa 1.8 million. Primary care registered patients with at least one of three chronic diseases, coronary heart disease, diabetes and stroke, underwent incentivised depression screening using the Hospital Anxiety and Depression Score (HADS).

125143 patients were identified with at least one chronic disease. 10670 (8.5%) were under treatment for depression and exempt from screening. Of remaining, HADS were recorded for 35537 (31.1%) patients. 7080 (19.9% of screened) had raised HADS (≥8); majority had indications of mild depression with HADS between 8 and 10. Over 6 months, 572 (8%) of those with raised HADS (≥8) were initiated on antidepressants, while 696 (2.4%) patients with normal HADS (<8) were also initiated on antidepressants (relative risk of antidepressant initiation with raised HADS 3.3 (CI 2.97-3.67), p value <0.0001). Of those with multimorbidity who were screened, 24.3% had raised HADS (≥8). A raised HADS was more likely in females, socioeconomically deprived, multimorbid or younger (18-44) individuals. Females and 45-64 years old were more likely to receive antidepressants.

Limitations

retrospective study of routinely collected data.

Conclusions

Despite incentivisation, only a minority of patients underwent depression screening, suggesting that systematic depression screening in chronic disease can be difficult to achieve in routine practice. Targeting those at greatest risk such as the multimorbid or using simpler screening methods may be more effective. Raised HADS was associated with higher number of new antidepressant prescriptions which has significant resource implications. The clinical benefits of such screening remain uncertain and merits investigation.

Parent-infant vocalisations at 12 months predict psychopathology at 7 years

This study investigated the utility of adult and infant vocalisation in the prediction of child psychopathology. Families were sampled from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. Vocalisation patterns were obtained from 180 videos (60 cases and 120 randomly selected sex-matched controls) of parent-infant interactions when infants were one year old. Cases were infants who had been subsequently diagnosed aged seven years, with at least one psychiatric diagnostic categorisation using the Development and Wellbeing Assessment. Psychopathologies included in the case group were disruptive behaviour disorders, oppositional-conduct disorders, Attention Deficit Hyperactivity Disorder, pervasive development disorder, and emotional disorders. Associations between infant and parent vocalisations and later psychiatric diagnoses were investigated. Low frequencies of maternal vocalisation predicted later development of infant psychopathology. A reduction of five vocalisations per minute predicted a 44% (95%CI: 11-94%; p-value=0.006) increase in the odds of an infant being a case. No association was observed between infant vocalisations and overall case status. In sum, altered vocalisation frequency in mother-infant interactions at one year is a potential risk marker for later diagnosis of a range of child psychopathologies.

Soluble ST2 associates with diabetes but not established cardiovascular risk factors: a new inflammatory pathway of relevance to diabetes?

Preliminary data mostly from animal models suggest the sST2/IL-33 pathway may have causal relevance for vascular disease and diabetes and thus point to a potential novel inflammatory link to cardiometabolic disease. However, the characterisation of sST2 levels in terms of metabolic or vascular risk in man is completely lacking. We sought to address this gap via a comprehensive analysis of risk factor and vascular correlates of sST2 in a cross-sectional study (pSoBid). We measured sST2 in plasma in 639 subjects and comprehensively related it to cardiovascular and diabetes risk factors and imaged atherosclerosis measures. Circulating sST2 levels increased with age, were lower in women and in highest earners. After adjusting for age and gender, sST2 levels associated strongly with markers of diabetes, including triglycerides [effect estimate (EE) per 1 standard deviation increase in sST2:1.05 [95%CI 1.01,1.10]), liver function (alanine aminotransaminase [ALT] and γ-glutamyl transferase [GGT]: EE 1.05 [1.01,1.09] and 1.13 [1.07,1.19] respectively), glucose (1.02 [1.00,1.03]) and sICAM-1 (1.05 [1.02,1.07]). However, sST2 levels were not related to smoking, cholesterol, blood pressure, or atheroma (carotid intima media thickness, plaque presence). These results suggest that sST2 levels, in individuals largely without vascular disease, are related principally to markers associated with diabetes and ectopic fat and add support for a role of sST2 in diabetes. Further mechanistic studies determining how sST2 is linked to diabetes pathways may offer new insights into the inflammatory paradigm for type 2 diabetes.

Regulation of synaptic connections in the rabbit ciliary ganglion

One of the intriguing questions about the establishment of synaptic connections is how appropriate numbers of different axons come to innervate each target neuron. A reorganization of connections in early postnatal life appears to be an important aspect of this process, since many of the axons terminals that initially innervate target cells are subsequently lost. The rabbit ciliary ganglion is a remarkably simple neural ensemble in which to examine this rearrangement of developing synaptic connections. Using this system we have found that a reduction in the number of axons innervating each cell occurs without any change in the number of ciliary ganglion cells or preganglionic neurons; therefore the rearrangement is not based on cell death. The number of different axons that ultimately innervate each cell is, however, influenced in some way by the geometry of individual target neurons. Thus, mature ganglion cells that lack dendrites are generally innervated by a single axon, while neurons with increasingly complex dendritic arbors receive innervation from a commensurate number of different axons. At birth, on the other hand, neurons with or without dendritic processes receive about the same number of preganglionic inputs. These results suggest that the geometry of the target cell influences the competitive interaction between different axons innervating the same neuron. Indeed, an important function of dendrites may be to regulate the number of axons that innervate each nerve cell.

Does PTSD occur in sentenced prison populations? A systematic literature review

BACKGROUND

A systematic review of the literature on mental disorder in prisoners, published in 2002, made no mention of post-traumatic stress disorder (PTSD), but indicators from other studies suggest that a history of serious and chronic trauma is common among offenders.

AIMS

To conduct a systematic review of the literature with the specific questions: does any epidemiological study of sentenced prisoners include data on prevalence of PTSD while in prison? If so, what is the prevalence in this group?

METHOD

Literature databases EMBASE, Medline, PsychInfo, PILOTS and SIGLE were searched. The Journal of Traumatic Stress was searched manually. Preliminary screening was conducted by reading abstracts of hundreds of papers. Ten exclusion criteria were then applied to the screened selection. Reference sections of all accessed papers were searched for any further studies.

RESULTS

One hundred and three potentially relevant papers were identified after preliminary screening. Four met all criteria for inclusion and suffered none of the exclusion criteria. PTSD rates ranged from 4% of the sample to 21%. Women were disproportionately affected.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

All four papers suggested that the prevalence of PTSD among sentenced prisoners is higher than that in the general population, as reported elsewhere. Overall the findings suggest a likely need for PTSD treatment services for sentenced prisoners.

An empirical explanation of the Chubb illusion

The perceived difference in brightness between elements of a patterned target is diminished when the target is embedded in a similar surround of higher luminance contrast (the Chubb illusion). Here we show that this puzzling effect can be explained by the degree to which imperfect transmittance is likely to have affected the light that reaches the eye. These observations indicate that this 'illusion' is yet another signature of the fundamentally empirical strategy of visual perception, in this case generated by the typical influence of transmittance on inherently ambiguous stimuli.

A wholly empirical explanation of perceived motion

Because the retinal activity generated by a moving object cannot specify which of an infinite number of possible physical displacements underlies the stimulus, its real-world cause is necessarily uncertain. How, then, do observers respond successfully to sequences of images whose provenance is ambiguous? Here we explore the hypothesis that the visual system solves this problem by a probabilistic strategy in which perceived motion is generated entirely according to the relative frequency of occurrence of the physical sources of the stimulus. The merits of this concept were tested by comparing the directions and speeds of moving lines reported by subjects to the values determined by the probability distribution of all the possible physical displacements underlying the stimulus. The velocities reported by observers in a variety of stimulus contexts can be accounted for in this way.

Why we see things the way we do: evidence for a wholly empirical strategy of vision

Many otherwise puzzling aspects of the way we see brightness, colour, orientation and motion can be understood in wholly empirical terms. The evidence reviewed here leads to the conclusion that visual percepts are based on patterns of reflex neural activity shaped entirely by the past success (or failure) of visually guided behaviour in response to the same or a similar retinal stimulus. As a result, the images we see accord with what the sources of the stimuli have typically turned out to be, rather than with the physical properties of the relevant objects. If vision does indeed depend upon this operational strategy to generate optimally useful perceptions of inevitably ambiguous stimuli, then the underlying neurobiological processes will eventually need to be understood within this conceptual framework.

The relevance of visual perception to cortical evolution and development

The quality of brightness--perhaps the simplest visual attribute we perceive--appears to be determined probabilistically. In this empirical conception of the perception of light, the stimulus-induced activity of visual cortical neurons does not encode the retinal image or the properties of the stimulus per se, but associations (percepts) determined by the relative probabilities of the possible sources of the stimulus. If this theory is correct, the rationale for the prolonged postnatal construction of visual circuitry--and the evolution of this visual scheme--is to strengthen and/or create by activity-dependent feedback the empirically determined association on which vision depends.

An empirical explanation of color contrast

For reasons not well understood, the color of a surface can appear quite different when placed in different chromatic surrounds. Here we explore the possibility that these color contrast effects are generated according to what the same or similar stimuli have turned out to signify in the past about the physical relationships between reflectance, illumination, and the spectral returns they produce. This hypothesis was evaluated by (i) comparing the physical relationships of reflectances, illuminants, and spectral returns with the perceptual phenomenology of color contrast and (ii) testing whether perceptions of color contrast are predictably changed by altering the probabilities of the possible sources of the stimulus. The results we describe are consistent with a wholly empirical explanation of color contrast effects.

Why are angles misperceived?

Although it has long been apparent that observers tend to overestimate the magnitude of acute angles and underestimate obtuse ones, there is no consensus about why such distortions are seen. Geometrical modeling combined with psychophysical testing of human subjects indicates that these misperceptions are the result of an empirical strategy that resolves the inherent ambiguity of angular stimuli by generating percepts of the past significance of the stimulus rather than the geometry of its retinal projection.

Color vision and the four-color-map problem

Four different colors are needed to make maps that avoid adjacent countries of the same color. Because the retinal image is two dimensional, like a map, four dimensions of chromatic experience would also be needed to optimally distinguish regions returning spectrally different light to the eye. We therefore suggest that the organization of human color vision according to four-color classes (reds, greens, blues, and yellows) has arisen as a solution to this logical requirement in topology.

The effects of color on brightness

Observation of human subjects shows that the spectral returns of equiluminant colored surrounds govern the apparent brightness of achromatic test targets. The influence of color on brightness provides further evidence that perceptions of luminance are generated according to the empirical frequency of the possible sources of visual stimuli, and suggests a novel way of understanding color contrast and constancy.