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 Quartile1.62 (1.18–2.25)0.003
    3rd Quartile1.38 (0.99–1.92)0.05
    4th Quartile1.74 (1.26–2.40)0.001
    Trend1.15 (1.04–1.27)0.005
Depressive symptoms (SMFQ) at 17 (n = 2145)
    2nd Quartile0.95 (0.71–1.26)0.73
    3rd Quartile0.90 (0.68–1.21)0.49
    4th Quartile1.08 (0.82–1.43)0.59
    Trend1.02 (0.93–1.12)0.68
Depressive symptoms (SMFQ) at 19 (n = 1570)
    2nd Quartile0.74 (0.52–1.04)0.08
    3rd Quartile0.81 (0.58–1.12)0.20
    4th Quartile1.06 (0.76–1.46)0.74
    Trend1.02 (0.92–1.14)0.70
Depression (CIS-R) at 18 (n = 1910)
    2nd Quartile0.84 (0.55–1.28)0.41
    3rd Quartile0.83 (0.54–1.26)0.37
    4th Quartile1.14 (0.76–1.70)0.53
    Trend1.04 (0.91–1.19)0.57
  • SMFQ, Short Moods and Feelings Questionnaire; CIS-R, Clinical Interview Schedule-Revised.