Table 1

Demographic characteristics, substance use and risky sexual behaviour in late and early adolescence in both cohorts

Analyses of later adolescent substance use and multiple sexual partners					Analyses of earlier adolescent substance use and early sexual initiation
Mean age (SD)	1987/1990 (‘earlier’) cohort		1999/2003 (‘later’) cohort		Mean age (SD)	1987/1990 (‘earlier’) cohort		1999/2003 (‘later’) cohort
	18 years 7 months (3.9 months)		19 years 3 months (6.4 months)			15 years 8 months (3.8 months)		15 years 5 months (3.7 months)
	N	%	N	%		N	%	N	%
Total	887	100	910	100	Total	884	100	933	100
Gender					Gender
Male	418	47.1	454	49.9	Male	416	47.0	473	50.7
Female	469	52.9	456	50.1	Female	468	53.0	460	49.3
Social class					Social class
Non-manual	378	42.6	410	45.1	Non-manual	375	42.4	408	43.8
Manual	509	57.4	499	54.9	Manual	509	57.6	525	56.2
Current smoker^*					Started smoking at age <14^*
Yes	298	33.6	308	33.9	Yes	193	21.9	195	20.9
No	589	66.4	602	66.1	No	691	78.1	738	79.1
Excessive drinking^*^†					Monthly drinking at age 15^‡
Yes	181	20.4	295	32.4	Yes	175	19.8	600	64.3
No	706	79.6	615	67.6	No	709	80.2	333	35.7
Ever used illicit drugs^*					Ever illicit drugs at age 15^‡
Yes	288	32.5	532	58.5	Yes	85	9.6	391	41.9
No	599	67.5	378	41.5	No	799	90.4	542	58.1
3+ sexual partners^*					Sex at age <16^*
Yes	212	23.9	453	49.8	Yes	139	15.7	265	28.4
No	675	76.1	456	50.2	No	745	84.3	668	71.6

↵* Information obtained during interview at age 18–19.
↵† Defined as ≥22 units in the past week for boys, ≥15 units for girls.
↵‡ Information obtained during interview at age 15 (earlier cohort) or self-completion questionnaire (later cohort).