Purpose: Previous studies have emphasised that women with pre-existing mood disorders are more inclined to discontinue hormonal contraceptive use. However, few studies have examined the effects of combined oral contraceptives (COC) on mood in women with previous or ongoing mental disorders. Materials and methods: This is a supplementary analysis of an investigator-initiated, double-blinded, randomised clinical trial during which 202 women were treated with either a COC (1.5mg estradiol and 2.5mg nomegestrolacetate) or placebo during three treatment cycles. The Mini International Neuropsychiatric Interview was used to collect information on previous or ongoing mental disorders. The primary outcome measure was the total change score in five mood symptoms on the Daily Record of Severity of Problems (DRSP) scale in the intermenstrual phase of the treatment cycle. Results: Women with ongoing or previous mood, anxiety or eating disorders allocated to COC had higher total DRSP -scores during the intermenstrual phase of the treatment cycle in comparison with corresponding women randomised to placebo, mean difference 1.3 (95% CI 0.3-2.3). In contrast, among women without mental health problems, no difference in total DRSP -scores between COC- and placebo users was noted. Women with a risk use of alcohol who were randomised to the COC had higher total DRSP -scores than women randomised to placebo, mean difference 2.1 (CI 95% 1.0-3.2). Conclusions: Women with ongoing or previous mental disorders or risk use of alcohol have greater risk of COC-induced mood symptoms. This may be worth noting during family planning and contraceptive counselling.