Table 2.

Mendelian randomisation analyses: odds ratios for depressive symptoms at ages 14, 17 and 19 years (SMFQ⩾11), and for depression diagnosis consistent with ICD-10 criteria at age 18, by continuous and categorical risk scores

	OR (95% CI)	P
Continuous risk score
SMFQ at 14 (n = 2404)	1.02 (1.005–1.04)	0.01
SMFQ at 17 (n = 2145)	1.002 (0.99–1.02)	0.78
SMFQ at 19 (n = 1570)	1.001 (0.98–1.02)	0.88
CISR at 18 (n = 1910)	1.004 (0.98–1.03)	0.73
Categorical risk score
Depressive symptoms (SMFQ) at 14 (n = 2404)
2nd Quartile	1.62 (1.18–2.25)	0.003
3rd Quartile	1.38 (0.99–1.92)	0.05
4th Quartile	1.74 (1.26–2.40)	0.001
Trend	1.15 (1.04–1.27)	0.005
Depressive symptoms (SMFQ) at 17 (n = 2145)
2nd Quartile	0.95 (0.71–1.26)	0.73
3rd Quartile	0.90 (0.68–1.21)	0.49
4th Quartile	1.08 (0.82–1.43)	0.59
Trend	1.02 (0.93–1.12)	0.68
Depressive symptoms (SMFQ) at 19 (n = 1570)
2nd Quartile	0.74 (0.52–1.04)	0.08
3rd Quartile	0.81 (0.58–1.12)	0.20
4th Quartile	1.06 (0.76–1.46)	0.74
Trend	1.02 (0.92–1.14)	0.70
Depression (CIS-R) at 18 (n = 1910)
2nd Quartile	0.84 (0.55–1.28)	0.41
3rd Quartile	0.83 (0.54–1.26)	0.37
4th Quartile	1.14 (0.76–1.70)	0.53
Trend	1.04 (0.91–1.19)	0.57

SMFQ, Short Moods and Feelings Questionnaire; CIS-R, Clinical Interview Schedule-Revised.