Schizophrenia is consistently associated with lower IQ compared to the IQ of control groups, or estimated premorbid IQ. It is not likely that the IQ scores deteriorate during the prodromal phase or first psychotic episode; they are already present before the onset of the prodromal phase and have been detected in childhood.

We investigated cognitive functioning and IQ levels in a group of 36 patients with schizophrenia or other psychotic disorders.

The IQ scores in our sample were lower than average. The IQ showed a relation with attention, memory, speed of information processing and some aspects of executive functioning. However, when IQ scores were corrected for processing speed, they were no longer below average.

These findings are important in considering the value of intelligence levels in schizophrenia. IQ scores should be judged in combination with cognitive functioning and school career to assess a patients capabilities in society. Cognitive functions and other variables might have a considerable influence on IQ scores. This rises the question of whether the low IQ scores are a primary or secondary deficit. Schizophrenia patients may have normal IQs, but could be less capable of making an IQ-test.

There are insufficient data from nationwide surveys on the prevalence of specific psychotic disorders and associated co-morbidities.

The 2010 Australian national psychosis survey used a two-phase design to draw a representative sample of adults aged 18–64 years with psychotic disorders in contact with public treatment services from an estimated resident population of 1 464 923 adults. This paper is based on data from 1642 participants with an International Classification of Diseases (ICD)-10 psychotic disorder. Its aim is to present estimates of treated prevalence and lifetime morbid risk of psychosis, and to describe the cognitive, physical health and substance use profiles of participants.

The 1-month treated prevalence of psychotic disorders was 3.10 cases per 1000 population aged 18–64 years, not accounting for people solely accessing primary care services; lifetime morbid risk was 3.45 per 1000. Mean premorbid intelligence quotient was approximately 0.5 s.d.s below the population mean; current cognitive ability (measured with a digit symbol coding task) was 1.6 s.d.s below the population mean. For both cognitive tests, higher scores were significantly associated with better independent functioning. The prevalence of the metabolic syndrome was high, affecting 60.8% of participants, and pervasive across diagnostic groups. Of the participants, two-thirds (65.9%) were current smokers, 47.4% were obese and 32.4% were sedentary. Of the participants, half (49.8%) had a lifetime history of alcohol abuse/dependence and 50.8% lifetime cannabis abuse/dependence.

Our findings highlight the need for comprehensive, integrative models of recovery to maximize the potential for good health and quality of life for people with psychotic illness.