We’ve all heard the urban myth that long-term couples start to look more and more alike over time. After all, the more time you spend with someone, the more you pick up each other’s habits and turns of phrase. In fact, one 1987 study even found that decades of shared emotions and experiences could lead to similar wrinkle lines and facial features as couples aged together.

But now, a new study in Translational Psychiatry has shown that couples don’t just look more alike over time — they feel more alike, too. According to researchers from Charles University in Prague, long-term couples often exhibit similar mental health journeys over the course of their relationships.

To study whether couples experienced similar mental health trajectories over the course of their relationship, the researchers examined 11,136 heterosexual couples from Europe every two years for 12 years. 

In 76.9% of cases, couples experienced “consistently low depressive symptoms” every two years. In 7.2% of couples, depressive symptoms decreased over time. In 7.8% of cases, the couples experienced increasing depressive symptoms. In a further 8.1% of cases, only the women exhibited depressive symptoms. 

In other words, for the vast majority of couples, the mental health trajectories matched up, suggesting that when one person in a couple experiences a change in their mental health, this can influence their partner to experience a similar shift. 

Interestingly, it seems that heterosexual women are more prone to be influenced by their partner’s mental health than vice versa. “This is in accordance with recent findings that women were more susceptible to the emotional contagion of sadness than men (while no sex difference was found in happiness),” the researchers noted.

While many couples showed similar ups and downs, there were no couples who had consistently high depressive symptoms over the course of 12 years. “We speculate that people with mutually high depression probably do not initiate a relationship with each other or these couples are not stable, and their relationship quickly dissolute,” wrote the researchers.

While many of the couples who participated in the study experienced changes in their mental health at different rates, the study found that no couples were “truly divergent in depressive symptoms”. In other words, in almost every long-term couple, some “syncing up” is likely.

According to the researchers, understanding how your mental health might be linked to your partner’s can help you to avoid relationship problems further down the line. For instance, in the couples who experienced an increase in depressive symptoms over the course of their relationship, there was a high “prevalence of bereavement and relationship dissolution during subsequent assessment in comparison to the other classes”.

As the study notes, more research is needed to determine whether this phenomenon stems from people choosing partners with similar backgrounds or whether our mental health trajectory really is influenced by our partners. More research is also needed to discover whether this phenomenon occurs in non-Western countries at the same rate.

But, until then, it seems clear that for long-term couples, thinking about mental health in terms of the individual may not be as useful as we once thought — and chances are, your partner is going through something similar to you.

Images: Getty