CANNABIS USE IS ASSOCIATED WITH GREATER PSYCHOTIC SYMPTOMS AND INCREASED DEPRESSION

Christina ComelyJohn Howard

Kevin Vaughn Diba Pourmand

& Claire Wakefield

NSW Department of Corrective Services

Macquarie UniversityPalmerston Unit,

Hornsby Ku-ring-gai Hospital

“Cannabis opens up doors in my head that I

believe are closed for my own protection. If I

go through these doors, the voices tell me to

commit suicide...” Male participant, 33 y

rs, quit 3 years

‘I believe cannabis has a chemical reaction in the

brain and that it could have contributed to the

mental illness that I now have...’

Male participant, current user

Sample 3: Current cannabis users (n=16)

16 current cannabis users, the group comprised 3 heavy users (smoking more than once per day) and 13 mild users (smoking once per day or less). 93% of subjects indicated that they smoked hydroponically grown cannabis (approx 17% to 30% THC).

Sample 4: Ex-users of cannabis (n=15)

15 ex-users of cannabis, who had stopped cannabis use at least 4 months, but generally 2-5 years prior to interview.

Sample 5: Non-users of cannabis (n=14)

14 outpatients who did not have a significant cannabis use history (they had used it a maximum of ‘once or twice’).

Confounding factors were carefully controlled in this study. For samples 3 to 5 it was impossible to individually match the controls, but the control group had similar means on key descriptive variables and the remaining variability in age and sex was statistically controlled for. Analyses were also controlled for differences in alcohol and polydrug abuse despite the level of alcohol abuse and other drug use being comparatively low in the sample. Other potential confounding variables were assessed. Little difference between the three interviewed samples was found in relation to medication type and compliance and so it was considered unnecessary to control for these factors. The only significant demographic differences between cannabis users, ex-users and non-users were living situation and gender, the male rate of cannabis use was higher than the female rate.

Objective: To further investigate previous findings that the use of cannabis by people with a mental illness leads to higher rates of relapse to psychotic symptoms and worse relapse episodes.

Experiment 1: Data Base Comparison

In order to investigate the impact of cannabis use on recovery from mental illness we compared the rates of rehospitalisation and remaining in case management in first admission psychosis patients admitted to Hornsby Ku-ring-gai Hospital over a 10 year period.

Sample 1: Regular users of cannabis (n=63)

63 patients who, at admission, reported using cannabis at least weekly.

Sample 2: Non users of cannabis (n=96)

96 patients reported no cannabis use and were included in sample 2.

Table 1: Rehospitalisation index and rate of retention in case management of cannabis using patients compared to non-using controls. Current users (n=63) Non-users (n=96) Significance

Rehospitalisation

index 0.48 0.39 x2=5.11; p=.02

Rate of remaining in

case management 45.3% 24.7% x2 =8.36; p=.015

The rehospitalisation index was significantly higher for the cannabis-using group, indicating that the cannabis-using group was more likely to be rehospitalised after their initial discharge than the non-using group. As well, 45.3% of regular users were still in active case management in September 2000 compared with 24.7% of non-users, implying that the rate of recovery from psychiatric illness was slower in the cannabis-using group relative to the non-using group.

Experiment 2: Interviewed Samples

Self reported and clinician rated psychiatric symptoms were compared in three groups of psychiatric outpatients in order to investigate the impact of cannabis use on their experience of psychiatric symptoms. Potential subjects were excluded if they had a primary addiction to a drug other than cannabis or exhibited severely disturbed behaviour. Interviews were conducted at the hospital outpatient clinic, the CHC or the participant’s home, and were audio taped.

“It is a straightforward down hill process, it made you feel good but when you really looked at it something was broken into you (sic) …it’s a weird drug, you can’t explain it, it just brings you down socially, morally…. I had no self–esteem, …it effected my judgement, I couldn’t think, my concentration was totally blown out of the water…” Male ex-user, who later replied, ‘Yes all the time,’ when asked if it made him paranoid.

Results:

Brief Psychiatric Rating Scale (BPRS) (Ventura, Green, Shaner & Liberman, 1993).The scores for positive psychotic symptoms, depression and total BPRS score where highest for current users indicating that current users experienced more psychiatric symptoms than ex-users and non-users. (Statistical tests were corrected for alcohol and polydrug abuse, age and sex).

Table 2: Means of the 5 BPRS subscales and total BPRS scores for current users, ex-users and non-users (n=41*).

Positive Depression Negative Mania Disorient- Total BPRS

Symptoms Symptoms ation

Current users

(n=15) 11.06 12.26 6.8 7.9 2.26 37.0

Ex-users (n=13) 10.76 11.84 6.3 8.5 2.3 36.4

Non-users (n=13) 9.23 9.53 7 7.3 2 31.5

P .04 .004 Ns Ns Ns .004

Brief Psychiatric Rating Scales

Figure 1.1: BPRS scales: Means of Total BPRS scores, positive symptoms, depression, negative symptoms, mania and disorientation for current users, ex-users and controls.

Brief Psychiatric Rating Scale Items

Figure 1.2: Selected items from the 24 item BPRS. Means for current users, ex-users and controls of items 2 - anxiety, 3 - depression, 4 - suicidality, 5 - guilt, 6 - hostility, 10 - hallucinations and 11 - unusual thought content.

Brief Symptom Inventory Scores

Figure 2: Means of the 9 primary dimensions of the BSI for current users, ex-users and controls.

Brief Symptom Inventory ScoresTable 3: Means scores of the 9 primary symptom dimensions and Global Score Index of the Brief Symptom Inventory for current users, ex-users and non-users*. SOM OC IS DEP ANX HOS PHOB PAR PSY GSI Current users (n=16) 1.32 1.48 0.95 1.28 1.24 0.86 0.98 1.12 1.17 1.15 Ex-users (n=14)* 1.07 1.56 1.78 1.19 1.38 0.78 1.08 1.12 1.17 1.23 Non-users (n=14) 0.48 0.81 0.64 0.61 0.64 0.3 0.61 0.45 0.51 0.55 P .01 .02 .001 .02 .01 ns ns .002 .01 .007 Som = Somatization, OC = Obsessive- Compulsive, IS = Interpersonal Sensitivity, Dep = Depression, Anx = Anxiety, Hos = Hostility, Phob = Phobic Anxiety, Par = Paranoid Ideation, and Psy = Psychoticism, GSI = Global Score Index. * One BSI test for an ex-user was ruled invalid.

Correlation with years of cannabis use

BPRS total and depression subscale scores were significantly correlated with years of cannabis use (r= .3492, p