Substance Abuse and Psychosis
Clinical studies and community surveys document high rates of substance use disorders (SUD) in persons with psychotic symptoms. The lifetime prevalence of substance abuse among persons with psychotic illnesses such as schizophrenia and bipolar disorder is much higher than in the general population.
This comorbidity is most often associated with being male, single, young, and having a conduct or antisocial personality disorder. Persons with psychosis also tend to abuse multiple substances. The overlapping biological substrates responsible for this co-occurrence include structural brain abnormalities, genetic vulnerabilities, and early exposure to stress or trauma.
A high prevalence of substance abuse in persons with schizophrenia has been reported in numerous studies conducted in developed countries. According to the US National Institute of Mental Health, schizophrenia carries a 10.1 percent risk of drug abuse, and SUD may constitute the most common comorbidity of schizophrenia. Apart from tobacco and cannabis (the preferred substances), these persons also abuse alcohol, cocaine, and amphetamines.
When a person presents to mental health professionals with recent-onset psychosis associated with substance abuse, it becomes essential to establish whether the substance use caused the symptoms. Psychosis is considered to be independent of the SUD if the psychosis occurred before the substance use or if the psychosis persisted during long substance-free periods. An absence of disorientation (which occurs in substance-induced delirium) also may point to a distinct psychosis.
In practice, the aforementioned features can be difficult to ascertain. Persons with psychosis often do not remember the exact sequence of events that contributed to the development of their disorder. Therefore, it becomes difficult to pinpoint the temporal relationship of psychotic symptoms and substance abuse. In addition, the patients may not experience significant substance-free periods. The diagnosis dilemma is further amplified by the similarity of symptoms, such as paranoia and auditory hallucinations, occurring both in independent psychosis and in psychosis induced by substances (especially stimulants). For this reason, persons with comorbid psychosis and SUD need to be thoroughly assessed at presentation, detoxified, treated immediately by interdisciplinary teams (using pharmacotherapy and cognitive behavioral-therapy among other approaches), and then monitored.
Overall, coexisting SUD imparts a more severe character and a poorer outcome to psychotic disorders, with frequent relapses and hospitalizations. Studies show, for example, that persons with defined comorbid SUD and first-episode psychosis are likely to have poorer treatment response than those with psychosis alone.
Psychosis Triggers
Alcohol and illegal drugs (cannabis, amphetamines, cocaine, hallucinogens, and opiates) can cause psychosis, both during use and as a consequence of withdrawal. Severe psychiatric disorders appear to correlate with earlier and longer exposure to stimulants. This suggests the presence of a critical developmental stage, or a threshold effect, of the drug on psychosis development.
Up to 15 percent of cannabis users report psychotic symptoms immediately after use. The hypothesis that cannabis abuse also causes chronic schizophrenia-like psychosis has not been ruled out, although evidence remains insufficient. An increasing body of literature points to early exposure to cannabis as generating psychosis later in life. Cannabis use during adolescence is an independent risk factor for the onset of psychosis in adulthood (especially in at-risk subjects) and associates with an earlier onset of schizophrenia. Studies also suggest that heavy cannabis use precipitates psychotic relapses in persons with schizophrenia who previously achieved remission.
Psychotic symptoms with paranoia and suspiciousness are reported during cocaine use and withdrawal. The propensity to experience cocaine-induced psychosis has been linked to mutations in genes coding for proteins involved in dopaminergic transmission.
Methamphetamine use is commonly associated with psychiatric conditions such as psychosis and depression. During both abstinent and intoxicated circumstances, persons who are methamphetamine-dependent are more likely to report psychotic symptoms than are cocaine addicts. Drug-induced psychotic syndromes are both positive (auditory hallucinations, persecutory delusions) and negative (poor speech, flattened affect). These psychotic states persist after the pharmacological effects of the methamphetamine have subsided, and they reappear upon reinjection. Furthermore, under stressful conditions, persons with a history of methamphetamine psychosis undergo spontaneous recurrence of their psychotic symptoms. Methamphetamine psychosis might therefore associate with persistent structural or functional brain damage caused by repeated drug administration.
Psychosis Can Lead to Substance Abuse
It has been suggested that persons with schizophrenia may self-medicate with tobacco, alcohol, and drugs. The substances of abuse are often perceived as alleviating negative symptoms (such as depression and withdrawal), improving hallucinations and paranoid delusions, lessening adverse effects of medications (such as restlessness), and providing an avenue for social interaction. This causal relationship remains unclear, as some studies have contradicted the self-medication hypothesis for this comorbidity.
Bibliography
Emmelkamp, Paul M. G., and Ellen Vedel. Evidence-Based Treatment for Alcohol and Drug Abuse: A Practitioner’s Guide to Theory, Methods, and Practice. New York: Routledge, 2006. Print.
Tamminga, Carol A., et al., eds. Deconstructing Psychosis: Refining the Research Agenda for DSM-V. Arlington: Amer. Psychiatric Assn., 2010. Print.
Thakkar, Vatsal G. Addiction. New York: Chelsea, 2006. Print.
Volkow, Nora D. “Substance Use Disorders in Schizophrenia: Clinical Implications of Comorbidity.” Schizophrenia Bulletin 35 (2009): 469–72. Print.
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