The emergence of depressive symptoms from late childhood into adolescence in the ALSPAC cohort: impact of age, gender and puberty Carol Joinson, Jon Heron 1, Tim Croudace 2, Ricardo Araya, Glyn Lewis Department of Community Based Medicine, 1 Department of Social Medicine, 2 University of Cambridge Avon Longitudinal Study of Parents and Children ALSPAC

Prevalence of depression in boys and girls from childhood to adolescence Pre-adolescence: similar rates of depression in boys and girls. Marked increase in rates of depression in girls during early adolescence. By mid-adolescence around twice as many girls than boys with depression.

Gender difference in depression Gender difference persists throughout most of adult life; major concern to public health. Early depression has a chronic and recurrent course; increased risk of future adverse outcomes. Need for systematic longitudinal research to increase understanding of the factors associated with female rise in depression during adolescence.

Pubertal status Pubertal status= level of physical maturation. Key predictor of rising adolescent depression / emerging gender difference. Advancing pubertal development associated with higher rates of depression & depressive symptoms in girls (no consistent association in boys).

Pubertal timing Pubertal timing= pubertal status relative to age. Higher levels of depression & depressive symptoms in girls who mature earlier than their peers. Onset of menarche is an important transition point for the female rise in depression Girls who experience menarche earlier their peers are more vulnerable to developing depressive symptoms in adolescence.

Background Research grant from the ESRC to examine risk factors for depressive symptoms in adolescence. Overall aim is to increase understanding of the impact of gender, pubertal development and environmental adversities on the emergence of depressive symptoms. Age, gender, pubertal status & pubertal timing.

Methods Participants: n=5002 from ALSPAC. Outcome variables: Self-reported depressive symptoms from the Short Mood and Feelings Questionnaire at 10.5, 13, 14 & 16 years. Explanatory variables: Pubertal status (Tanner stages); Timing of menarche [early =11.5 years & =13.5 years]. Potential confounders: Socioeconomic disadvantage; father absence; BMI.

Statistical analysis 1)Prevalence of high levels of depressive symptoms from age years (binary measure: defined as scores on SMFQ>=11). 2)Association between pubertal status and depressive symptom levels (continuous latent factors) at 3 time- points (10.5, 13 and 14 years). 3)Association between timing of menarche (early, normative, late) and continuous latent factors of depressive symptoms in a structural equation model.

(1) Prevalence of depressive symptoms Results

Prevalence of high levels of depressive symptoms from late childhood through adolescence in the ALSPAC cohort % with high levels of depressive symptoms (SMFQ>=11) Age in years

(2) Pubertal status and depressive symptoms

With increasing age, the association between advancing pubertal status and depressive symptoms in girls strengthens. Evidence for a linear relationship at 14 years. Advancement of each pubertal stage represents an increase in 0.13 SD's of depressive symptoms. Depressive symptoms Tanner stage (breast development) 10.5 years Depressive symptoms and pubertal status in girls Latent depressive symptom factors at 13 & 14 years are standardised to the metric of the first time-point (10.5 years) so the level of depressive symptoms can be compared across time points. 13 years 14 years

Depressive symptoms and pubertal status in boys Depressive symptoms 10.5 years 13 years 14 years Tanner stage (genital development)

(3) Timing of menarche and depressive symptoms

Mean depressive symptom scores at three time-points across groups defined by timing of menarche (early, normative and late) F = 0.19 (p =0.823)F = 8.06 (p < 0.001)F = (p < 0.001)

Time 1 (10.5 years) Time 2 (13 years) Time 3 (14 years) Timing of menarche early0.01 [-0.14, 0.16]0.24 [0.08, 0.36]0.19 [0.04, 0.35] normative0.00 ref late0.03 [-0.10, 0.16]-0.04 [-0.18, 0.11]-0.20 [-0.34, -0.06] p= 0.90p= 0.007p< Adjusted estimates of differences in depressive symptoms across timing of menarche groups Regression coefficients represent differences in symptom levels in terms of SD effect sizes (Cohen’s d) across the 3-level timing of menarche variable. All estimates referenced against the group with normative timing of menarche.

Overall findings Adolescence is characterised by a marked rise in rates of depressive symptoms in girls compared to boys. Expected 2:1 gender ratio in prevalence of high levels of depressive symptoms in females compared to males by age 16 years. More advanced pubertal status was associated with an increased level of depressive symptoms in girls but not boys. Earlier age at menarche is associated with increased levels of depressive symptoms in adolescence.

How does pubertal change exert an influence on levels of depressive symptoms in girls? Direct effects of pubertal hormones on the brain (e.g. rising oestrogen levels). Indirect effects of physical/biological pubertal changes mediated by psychological and social factors (e.g. biological/temperamental predisposition; interpersonal stressors; adversities; gender intensification). Early maturing girls faced with stressors / demands that that are inconsistent with their level of cognitive and emotional development.

Study strengths Large sample size. Longitudinal design. Regular reports of pubertal development from late childhood to adolescence. Data on potential confounders.

Study limitations Sample attrition has important implications for the internal validity of this study. Attrition in ALSPAC is strongly associated with socioeconomic disadvantage). Results consistent over the different samples employed so we feel the conclusions are robust in spite of the differential dropout.

Future directions Longer-term impact of early timing of menarche on rates of depressive symptoms and diagnosed depression. Potential mediating/moderating variables e.g. stressful life events, conflicts with peers and parents, body image/BMI, and self-concept.

Acknowledgements My colleagues: Jon Heron, Glyn Lewis, Ricardo Araya, Tim Croudace. The Economic and Social Research Council: RES The ALSPAC study team. The ALSPAC families. Contact details: