Objectives:
The purpose of this study was to examine the levels of depression and anxiety of lesbian and bisexual (LB) mothers raising children from a previous heterosexual relationship in a current same-sex relationship, on the basis of minority stress theory.

Methods:
58 LB biological mothers, 33 LB co-mothers from same-sex relationships and 60 mothers from different-sex marriages participated in a questionnaire-based online survey. The groups were compared in terms of depression and anxiety severity (state and trait). In the LB groups, correlation analysis was conducted between the dependent variables and the number of encountered negative homophobic events, the expectation of rejection, self-concealment, and internalised homophobia. To examine whether the associations between these variables in LB biological mothers and co-mothers differed, moderation analysis was used.

Results:
The levels of depression and anxiety were similar across the groups. Among LB mothers, anxiety (state and trait) correlated mainly with internalised homophobia, whereas depression was linked to the expectation of rejection. Notably, among biological LB mothers, as opposed to co-mothers, there was an association between both depression and anxiety (state) and negative homophobic events.

Conclusions:
The lack of intergroup differences in levels of depression and anxiety, with correlations of these variables with minority stress, may indicate high resources (e.g. family resilience) of LB mothers. The cost of homophobic events is higher for LB biological mothers than for LB co-mothers. This may be attributed to the later emergence of non-heterosexual identity in LB biological mothers who have children from heteronormative relationships, leading to a heightened sense of threat when their custody rights are challenged.