Substance dependence and other mental illnesses co-exist in a proportion of patients attending health services and recent research has attempted to estimate and describe the phenomenon. Two such studies are described in this article.
Co-morbid drug use or psychiatric diagnosis among alcohol-dependent patients
Lyne and colleagues reviewed the records of patients presenting with co-morbid psychiatric diagnoses and drug use at a 12-bed alcohol treatment unit in a psychiatric teaching hospital in Dublin between 1995 and 2006.1 Patients were included if they were aged 44 years or under, remained in hospital for more than 28 days, and had a diagnosis of alcohol dependence.
The review of 465 records revealed that 38.9% patients had used drugs other than alcohol during their life and 34.2% had a documented history of a co-morbid psychiatric diagnosis. Cannabis (26.4%), cocaine (17.1%), and ecstasy (12.5%) were the most common substances reported. Just under 10% reported use of benzodiazepines or other sedatives and just under 6% had used heroin. The disease-specific rates were: 25.3% had a depressive disorder; 3.9% an anxiety disorder; 2.8% a bipolar affective disorder and 2.2% a psychotic disorder. A small proportion (3.7%) of patients had two or more psychiatric diagnoses alongside their alcohol dependence. Forty-eight (10.3%) patients had a documented history of deliberate self-harm, of whom 29 had a psychiatric diagnosis as well as alcohol dependence.
The median age of the study population was 37 years and the age range was 17–44 years. Just over three-fifths (61.1%) of patients were men; 203 (44.3%) of the patients were never married; and 38 (8.3%) were separated or divorced. The proportions of women with a history of depressive disorder, eating disorder and deliberate self-harm were significantly higher than those for men. The proportion of men with psychotic disorder was marginally higher than that of women. Deliberate self-harm was associated with lifetime drug (excluding alcohol) use. Ecstasy users were more likely to have a diagnosis of depression.
Cannabis use and non-clinical dimensions of psychosis in university students presenting to a student health clinic
Skinner and colleagues explored the relationship between cannabis use and self-reported dimensions of psychosis in a population of university students presenting for any reason to primary care.2
Fifteen thousand students were enrolled in undergraduate or postgraduate courses at the National University of Ireland, Galway, in 2008. One thousand and forty-nine (7%) students attended the Student Health Unit between April and October of that year and these completed self-report questionnaires on:
· demographic profile
· history of mental illness
· alcohol and other drug misuse
· non-clinical dimensions of psychosis [Community Assessment of Psychic Experiences (CAPE)]
· anxiety and depression [Hospital Anxiety and Depression Scale (HADS)].
The respondents may not be representative of the third-level student population. The average age of the respondents was 21.2 years (range 17–54); 82% were women; 94% were Irish; and 96% were single. Sixteen per cent sought professional help for emotional or psychiatric problems; 23% reported a family history of mental illness; and almost 5% reported a family history of psychotic illness.
Respondents reported drinking an average of 9.4 units (range 0–120) of alcohol per week and an average of 5.9 units (range 0–35) per sitting. Forty per cent (423) had smoked cannabis at least once in their life, of whom 327 reported use between 1 and 30 times and 86 reported use 30 or more times. The average age at first use of cannabis was almost 17 years (range 10–40). The rates of lifetime use of other drugs were: ecstasy 6.9%, cocaine 5.8%, magic mushrooms 5.1%, LSD 2.1% and heroin 0.1%.
Twenty one per cent had HADS scores of between 8 and 10 (borderline abnormal level) on the anxiety subscale and 15% had scores of 11 or above (abnormal level). Just under 3% reported borderline abnormal level on the depressive subscale and 1% reported abnormal level. The average weighted CAPE frequency score for negative symptoms was 1.57 (range 1–4), and for positive symptoms 1.29 (range 1–3).
The higher HADS anxiety scores were associated with a personal history of mental illness, a family history of psychiatric disorder and being female. The higher HADS depression scores were associated with a personal history of mental illness.
The CAPE positive psychotic symptom scores were associated with: personal history of mental illness, family history of psychiatric disorder, younger respondents and men. The CAPE negative psychotic symptom scores were associated with: personal history of mental illness and family history of psychiatric disorder. The CAPE depressive symptom scores were associated with: a personal history of mental illness, a family history of psychiatric disorder and being female.
After controlling for the effects of personal history of mental illness, family history of psychiatric disorder, age and gender, the CAPE positive and negative psychotic symptom scores were associated with high frequency cannabis use. In addition, the CAPE negative psychotic symptom scores and depressive symptom scores were associated with low frequency cannabis use.
After further controlling for frequency of cannabis use, it was found that the earlier the age at which a person commenced cannabis use the more positive psychotic symptoms they experienced.
These findings support the hypotheses that cannabis use increases the risk of developing psychotic symptoms and that this risk is further increased in individuals who use cannabis more heavily and commence use at a younger age.
1. Lyne J, O Donoghue B, Clancy M and O’Gara C (2011) Comorbid psychiatric diagnoses among individuals presenting to an addiction treatment program for alcohol dependence. Substance Use & Misuse, 46(4): 351–358.
2. Skinner R, Conlon L, Gibbons D and McDonald C (2011) Cannabis use and non-clinical dimensions of psychosis in university students presenting to primary care. Acta Psychiatrica Scandinavica, 123(1): 21–27.