Hormonal contraceptives cause depression

This large study of over 264,000 UK women found that starting oral contraceptives was linked to a higher chance of being diagnosed with depression, mainly in the first two years.

• The percentage of women with depression in the first two years is not stated, but the difference in depression between the two groups is 9.94% (OC users) vs 8.65% (never used). Not all women will experience depression; this is more of a risk/side effect type of event.
• The study covers oral contraceptives only — not patches, implants, hormonal IUDs, or injections, so the broader claim about "hormonal contraceptives" goes beyond what was tested.
• Women who started OCs were younger and had more PCOS. This was adjusted, but it is difficult to remove this from the model completely.
• There is no correction for why women started OCs in the first place, which can bias the study toward other factors rather than the use of OCs.
• Women who started OCs as teenagers carried a heightened depression risk even years after stopping, while adult starters did not.
• The study is observational — the sibling analysis adds more controlled analysis, but it is not causal.
• The UK Biobank population is healthier and more predominantly White than the general public, and most OC use in this cohort occurred in the 1970s–80s with older pill formulations.