Cannabis induced psychosis and subsequent psychiatric disorders

Introduction: Long term change in diagnosis of patients having Cannabis induced psychosis (CIP) at the index evaluation is well recognised. Some patients are known to achieve complete remission while others go on to develop independent schizophrenia or mood disorders. Aims: To study the long-term course of CIP and factors influencing it. Method: Patients diagnosed as CIP (ICD 10: F12.5), admitted at NIMHANS, a tertiary neuropsychiatry centre at Bangalore, over the past 10 years were identified from medical records. 200 case records were identified and screened in detail. 57 met inclusion criteria and 35 patients could be followed up. Mean follow up duration was 5.75 years. Results: Patients who completely abstained from cannabis after the 1st episode had no relapse of psychiatric illness. They showed marked improvement in socio-occupational functioning as well. All those who relapsed to cannabis use had a recurrence of illness. Half the patients with predominantly non-affective psychosis progressed to an independent psychiatric disorder; while only 7.7% patients with predominantly affective psychosis developed an independent disorder (p = 0.01). Besides this, early onset of cannabis use (<= 18 years), younger age at onset of 1 st episode, positive family history of psychiatric illness, being unmarried and lower socio-economic status were associated with poor prognosis. Abstinence later in the course of illness did not improve outcome significantly. Conclusion: Abstaining from cannabis early in the course of illness is critical for good recovery. The course of CIP is variable and categorising CIP into affective vs. non-affective psychosis can be useful in clinical practice.