APIM analysis
We screened 397 infertile couples among 1022 subjects for inclusion in the APIM with distinguishable dyads. The results showed that both female and male chronotype exerted an actor effect on their own depressive symptoms (β = -0.514, p  <0.001; β = -0.228,p  <0.045, respectively). However, contrary to our expectations, our study did not observe a strong partner effect of female/male chronotype on spouse depressive symptoms. Specifically, the earlier chronotype for husband had a detrimental effect on wife’s depressive symptoms (β = 0.145, p  = 0.200), yet the earlier chronotype for the wife had a protective effect on husband’s depressive symptoms (β = -0.074, p  = 0.577), but neither was statistically significant (Table 3 ).