Background. Delusional disorder (DD) and obsessive–compulsive disorder (OCD) have been investigated in previous studies using probabilistic reasoning paradigms and abnormalities in each group have been reported. No study to date has compared results between these groups. This study compares patients with these disorders with those who have both phenomena.

Methods. Thirty subjects with DD, 29 with OCD and 16 with obsessive and delusional features were compared with 30 normal controls in a study of probabilistic reasoning using two different computer-based tasks involving a Bayesian paradigm.

Results. Deluded subjects showed a ‘jump to conclusions’ reasoning style, but on a test that added a consequence to their choices did not differ from normals. OCD subjects deviated from Bayesian and control norms to a greater degree than did DD subjects. In subjects with mixed psychopathology, the presence of both phenomena appeared to ‘normalize’ these probability estimates.

Conclusions. Our findings extend those of others but require cautious interpretation as to the role of probabilistic reasoning in the genesis of delusions or obsessions. Obsessionals in both the OCD and Mixed groups, showed substantial deviation from Bayesian norms, suggesting that obsessionality leads to a reasoning style that is less ‘normal’ than that of delusionals. Further work is required to investigate clinical correlates of these findings which provide modest support for the proposal that the combination of obsessions and delusions confers greater functional advantages than simply having delusions or obsessions.

Background. Previous studies have shown that individuals with autism show impaired performance on tests of executive function (Ozonoff et al. 1991, 1993; Hughes & Russell, 1993; Hughes et al. 1994). There is also strong evidence for genetic involvement in autism (see Rutter, 1991 for review). If executive dysfunction is a core impairment in autism, then similar impairments are hypothesized to exist in a subtler form among the parents of autistic children.

Methods. Forty parents of autistic children were compared with 40 parents of learning disabled children and 36 adults from unaffected families on three computerized tests of executive function. These tasks tapped attentional-shifting skills, visuospatial planning and working memory. Participants also received a computerized control test of spatial memory-span. In addition, the interviewer's initial impressions of family members were coded using a new 33-item questionnaire.

Results. A significant proportion of parents of autistic children (especially fathers) showed impaired executive function. By contrast, parents did as well as both comparison groups on a control test of spatial span, and on other ‘non-executive’ measures from the tasks, indicating that the autism group were as able and motivated as comparison groups. Interestingly, impairment of executive function was significantly correlated with the interviewer's pre-test impression of social abnormality among parents of autistic children.

Conclusions. The hypothesis that a significant proportion of parents of autistic children show impaired executive function was supported. Parents showed good memory ability, but relatively poor planning skills and attentional flexibility. The extent to which this is an inherent trait in family members, rather than a reflection of the difficulties involved in caring for an autistic child, remains to be examined.

Background. The aim of the present study was to investigate neuropsychological functions in dementia of the Alzheimer type (DAT) with respect to morphological changes that were revealed by quantitative magnetic resonance imaging (MRI).

Methods. Twenty patients with DAT (NINCDS-ADRDA criteria) and 10 healthy age and sex matched controls were included. The neuropsychological function was evaluated on a test battery covering the severity of dementia, verbal and visual memory, concentration and attention, language skills and general intelligence as well as activities of daily living. 3D MRI sequences were acquired using a 1.5 T Siemens MAGNETOM. Whole brain volume, total intracranial volume (TIV), volume of the frontal and temporal lobes and volumes of the amygdalahippocampus complex (AHC) were assessed using the newly developed software NMRWin.

Results. Apart from TIV all morphometric parameters differed significantly between the diagnostic groups. AHC volumes discriminated best between the groups, with only a small overlap. AHC atrophy exceeded generalized atrophy. These findings were confirmed when the data were reanalysed after dividing the DAT patients into a mildly and moderately affected group. The severity of dementia was significantly correlated with the volumes of the AHC and the volumes of the temporal lobes bilaterally, but not with the whole brain volume and the volumes of the frontal lobes.

Conclusions. These results underline the important role of the temporal substructures for aetiology and progression of DAT. They indicate that the volume of the AHC can be monitored by MRI and may be used to follow up the disease process.

The Center for Epidemiologic Studies Depression scale (CES-D) has been widely used in studies of late-life depression. Psychometric properties are generally favourable, but data on the criterion validity of the CES-D in elderly community-based samples are lacking. In a sample of older (55–85 years) inhabitants of the Netherlands, 487 subjects were selected to study criterion validity of the CES-D. Using the 1-month prevalence of major depression derived from the Diagnostic Interview Schedule (DIS) as criterion, the weighted sensitivity of the CES-D was 100%; specificity 88%; and positive predictive value 13·2%. False positives were not more likely among elderly with physical illness, cognitive decline or anxiety. We conclude that the criterion validity of the CES-D for major depression was very satisfactory in this sample of older adults.

Unless positive responses are verified at a second stage of data collection, a questionnaire-based survey has limited ability to assess change in caseness in a longitudinal study of a condition of low prevalence, assuming imperfect validity of the survey instrument.

Applications are invited for awards for research on schizophrenia and bipolar disorder. They may be up to $75000 a year for studies involving human subjects and $50000 a year for other studies. The deadline for applications is 1 March 1997. Further details and application forms can be obtained from: Ms Patrice P. De Haven, Research Awards Coordinator, Stanley Foundation Research Awards Program, c/o NAMI, 200 North Glebe Road, Suite 1015, Arlington VA 22203-3754 USA.