Table 1. Participant characteristics.
| Controls (n = 9) | Relatives (n = 8) | Patients (n = 8) | |
| Mean Age (SD) | 31.4 (11.4) | 36.1 (12.0) | 31.1 (8.9) |
| Percentage male (n) | 55.6 (5) | 62.5 (5) | 75.0 (6) |
| Mean IQ (SD) | 102.8 (14.0) | 105.5 (11.8) | 102.7 (15.6) |
| Frequency of cannabis use* % (n) | |||
| Monthly or less | 33.3 (3) | 25.0 (2) | 25.0 (2) |
| Weekly | 11.1 (1) | 12.5 (1) | 12.5 (1) |
| Daily | 55.6 (5) | 62.5 (5) | 62.5 (5) |
| Cannabis use frequency in heaviest period** % (n) | |||
| Monthly or less | 22.2 (2) | 25.0 (2) | 0.0 (0) |
| Weekly | 11.1 (1) | 12.5 (1) | 12.5 (1) |
| Daily | 66.7 (6) | 62.5 (5) | 87.5 (7) |
| Mean age of onset of cannabis use (SD) | 16.8 (3.7) | 14.9 (2.9) | 15.4 (2.4) |
| Lifetime cannabis dependence*** % (n) | 44.4 (4) | 25.0 (2) | 87.5 (7) |
| Current cannabis dependence*** % (n) | 44.4 (4) | 12.5 (1) | 62.5 (5) |
| Weighted PANSS scores mean (SD) | |||
| Positive | 1.0 (0.0) | 1.0 (0.1) | 1.5 (0.7) |
| Negative | 1.0 (0.0) | 1.0 (0.1) | 1.1 (0.2) |
| Global | 1.2 (0.1) | 1.1 (0.1) | 1.2 (0.2) |
| Total | 1.0 (0.0) | 1.0 (0.1) | 1.1 (0.1) |
| Nicotine usea % (n) | |||
| 0 | 44.4 (4) | 25.0 (2) | 25 (2) |
| 1–10 | 22.2 (2) | 37.5 (3) | 25 (2) |
| 11–20 | 33.3 (3) | 37.5 (3) | 37.5 (3) |
| >20 | 0.0 (0) | 0.0 (0) | 12.5 (1) |
| Alcohol useb % (n) | |||
| 0–50 | 66.7 (6) | 50.0 (4) | 62.5 (5) |
| 50–150 | 33.3 (3) | 37.5 (3) | 0.0 (0) |
| 150 − 350 | 0.0 (0) | 12.5 (1) | 37.5 (3) |
| Other medication use % (n) | |||
| Yes | 0.0 (0) | 12.5 (1) | 25.0 (2) |
| No | 100.0 (9) | 87.5 (7) | 75.0 (6) |
| Use of contraceptives % (n) | |||
| Yes | 22.2 (2) | 12.5 (1) | 0.0 (0) |
| No | 77.8 (7) | 87.5 (7) | 100.0 (8) |
| Use of other drugsc % (n) | |||
| Yes | 44.4 (4) | 37.5 (3) | 37.5 (3) |
| No | 55.5 (5) | 62.5 (5) | 62.5 (5) |
Note. Percentages do not always total 100 due to rounding.
*
Refers to cannabis use in the last 12 months.
**
Refers to the frequency of cannabis used in the most intensive period of use as assessed with the CIDI.
***
Cannabis dependence according to the Structured Clinical Interview for DSM Disorders, lifetime and current (i.e. present in the last month).
a
Refers to number of cigarettes per day.
b
Refers to grams per week. Standard drink/unit size in the Netherlands contains 9.9 g of ethanol.
c
Refers to other drug use in the last 12 months (incl. cocaine, opiates, psychostimulants, and sedatives).