Regional updateCannabis induced psychosis and subsequent psychiatric disorders
Introduction
Cannabis is the most common illicit substance of abuse and the estimated prevalence of cannabis use in India is 3% in general population (Ray, 2004) and 11% among patients seeking treatment in the major centres across India (Murthy et al., 2010). Cannabis has been widely used across the world despite a growing body of evidence to suggest an association between cannabis and chronic psychosis (Andreasson et al., 1987, Le Bec et al., 2009). Studies have also shown that when taken by healthy volunteers, cannabis produces not just positive symptoms (paranoia & euphoria) but negative and cognitive symptoms as well; thereby mimicking typical features of Schizophrenia (D'Souza et al., 2004). Research has also indicated that 13% of cases of schizophrenia could be averted if all cannabis use were prevented (Zammit et al., 2002). Considering this close association, it is important to study what proportion of cases of Cannabis induced psychosis (CIP)1 progress to develop an independent psychiatric disorder.
Short term outcome studies on CIP have consistently shown that complete remission of psychotic symptoms occurs in most cases (Kulhalli et al., 2007, Tunving, 1985). However, the long term course of CIP is not so well studied. Niemi-Pynttari et al. (2013) followed up 125 patients of CIP and found their 8 year cumulative risk of developing a Schizophrenia spectrum disorder to be 46%. Arendt et al. (2005) followed up 535 patients of CIP for at least 3 years and found that 44.5% converted to Schizophrenia spectrum disorders. Two similar studies wherein the proportion of patients with CIP was high, have also reported a high rate of conversion to Schizophrenia spectrum disorders in the long run (Crebbin et al., 2009, Komuravelli et al., 2011). There is lack of similar long term studies from India, where cannabis is the second most commonly abused intoxicating substance, next only to alcohol.
The current study, a case record review, was conducted to look at the long term stability of diagnosis of cannabis induced psychosis among inpatients of a tertiary neuropsychiatry centre in India. This study also looked at the factors that can influence the long term diagnosis and prognosis.
Section snippets
Data collection
The study was initiated after obtaining ethical clearance from the institute ethics committee. The medical records of patients with a diagnosis of Cannabis Induced Psychotic Disorder (coded: F12.5 as per ICD 10) (World Health Organization, 1992) from January 2002 to October 2011 were obtained. Records of patients coded as having Cannabis Dependence were also screened. The case records contained notes of a detailed evaluation, wherein a postgraduate trainee evaluates the case through clinical
Results
Of the 57 patients eligible for the study, detailed interviews could be carried out in 35 patients. Nineteen could not be traced due to inadequate contact details or shifting of place of residence. Another 3 patients refused consent to participate in the study. Among the 35 interviewed patients, 20 patients with regular follow-ups were interviewed at the hospital. Those who were not in regular follow up were contacted via telephone or home visit. Seven patients agreed for a home visit. Due to
Discussion
In our study, 34% of patients diagnosed with CIP at the time of first evaluation progressed to develop an independent psychiatric disorder at the end of 5.7 years (mean). This is slightly lower than the conversion rate of around 45% seen in the previous 2 studies on long term course of CIP done by Niemi-Pynttari et al. (2013). and Arendt et al. (2005). Rate of conversion was higher (50%) in the subset of patients with CIPD. Abstinence from cannabis use after the 1st episode itself was strongly
Funding
None.
Conflict of interest
None.
Acknowledgements
Toxicology Laboratory of Centre for Addiction Medicine for providing cannabis urine drug testing facility.
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