Table 1.

Descriptive statistics on frequency of cannabis use and cannabis symptom prevalence at baseline (n = 214) and 1-year follow-up (n = 197).

	Baseline	1-year follow-up
Past year frequency of cannabis use (%)
No use in past year	0.0	16.6
< Once per month	7.5	17.6
Once per month	1.9	2.1
2–3 times per month	6.6	6.7
Once per week	5.2	6.7
2–3 times per week	12.7	7.8
4–6 times per week	20.8	21.2
Daily	45.3	21.2
Past year DSM-IV cannabis abuse and dependence symptoms (%)
Abuse 1: role obligation	64.5	26.4
Abuse 2: hazardous use	51.4	39.1
Abuse 3: legal problems	3.7	2.0
Abuse 4: interpersonal problems	65.9	28.9
Dependence 1: tolerance	73.4	53.8
Dependence 2: use more/longer	22.4	5.6
Dependence 3: quit/cut down	62.6	39.1
Dependence 4: much time	77.6	47.7
Dependence 5: reduce activities	32.7	5.1
Dependence 6: psychological/physical	13.1	12.7
Mean DSM-IV cannabis abuse and dependence symptom count (SD)	4.7 (2.4)	2.4 (2.3)
Observed range of values	0–9	0–9
Cannabis withdrawal (past year) definitions (%)
Two-symptom recurrent cannabis withdrawal	37.4	21.3
Four-symptom recurrent cannabis withdrawal	17.8	11.2
LCA high severity recurrent cannabis withdrawal	17.3	10.6

Cannabis withdrawal is not included in the list of DSM-IV dependence symptoms in this table because DSM-IV does not specify how ‘cannabis withdrawal’ is to be identified. The total possible number of DSM-IV cannabis abuse and dependence symptoms is 10 (four abuse and six dependence symptoms). ‘LCA high severity’: latent class analysis-based definition of cannabis withdrawal that distinguishes youth in the LCA ‘high severity’ withdrawal class who reported recurrent episodes of withdrawal from all other participants. SD: standard deviation.