How common is psychosis?

According to a recent review article written by Peter Byrne (right), Early Intervention Team for Ealing, Southall, United Kingdom, and published in the British Medical Journal:

The one year prevalence of non-organic psychosis is 4.5 per 1000 community residents (Ref. 1). Most new cases arise in men under 30 and women under 35, but a second peak occurs in people over 60 years. Psychotic symptoms had a 10.1% prevalence in a non-demented community population over 85 years (Ref. 2). Schizophrenia has a one year prevalence of 3.3 per 1000 people, and a lifetime morbidity risk of 7.2 per 1000 people (Ref. w1). Independent of known associations with migration and ethnic origin, increased economic inequality in areas of high deprivation also predicts a higher incidence of schizophrenia (Ref. 3). Some people who become depressed (one in five of us over a lifetime) also develop hallucinations and delusions, related to and “congruent with” their low mood.

Bipolar affective disorder has a lifetime prevalence of 1.3-1.6% (Ref. 4), and it is characterised by episodes of psychosis during both high (“manic”) and low (depressive) relapses. The misuse of substances, notably cannabis (Ref. 5), raises the prevalence of psychotic symptoms further — substance misuse partly explains the 10 times higher prevalence of psychosis in prison populations (Ref. 1). Psychosis occurs frequently in all forms of dementia including Parkinson’s disease. Other causes of organic psychoses are neurological disorders (epilepsy, head injury, haemorrhage, infarction, infection, and tumours) and most causes of delirium.

Altogether, therefore, acute psychosis is one of the most common psychiatric emergencies. There are explanations of psychotic “symptoms” other than the biomedical model of this review; medicalising psychosis as “an illness like any other” increases both public pessimism about outcome and the stigma attached to people with psychosis (Ref. 6).

References:

1. Brugha T, Singleton N, Meltzer H, Bebbington P, Farrell M, Jenkins R, et al. Psychosis in the community and in prisons: a report from the British national survey of psychiatric morbidity. Am J Psychiatry 2005;162:774-80. (Download a free PDF of this paper by clicking here.)

2. Ostling S, Skoog I. Psychotic symptoms and paranoid ideation in a nondemented population-based sample of the very old. Arch Gen Psychiatry 2002;59:53-9. (Abstract available by clicking here.)

3. Boydell J, van Os J, McKenzie K, Murray RM. The association of inequality with the incidence of schizophrenia: an ecological study. Soc Psychiatry Psychiatr Epidemiol 2004;39:597-9. (Abstract available by clicking here.)

4. Müeller-Oerlinghausen B, Berghöfer A, Bauer M. Bipolar disorder. Lancet 2002;359:241-7. (Abstract available by clicking here.)

5. Henquet C, Krabbendam L, Spauwen J, Kaplan C, Lieb R, Wittchen HU, et al. Prospective cohort study of cannabis use, predisposition for psychosis, and psychotic symptoms in young people. BMJ 2005;330:11. (Abstract available by clicking here.)

6. Read J, Haslam N, Sayce L, Davies E. Prejudice and schizophrenia: a review of the “mental illness is an illness like any other” approach. Acta Psychiatr Scand 2006;114:303-18. (Abstract available by clicking here.)

w1. Saha S, Chant D, Welham J and McGrath J. A systematic review of the prevalence of schizophrenia. PLoS Med 2005; 2(5): e141. (Download a free PDF of this paper by clicking here.)