There are many other reasons to think that changes in our mental health and wellbeing may be damaging our sex lives. While Twenge, Sherman and Wells discounted both pornography use and work hours as causes behind the drops in sexual activity, the researchers argued the drops may be due to increasing levels of unhappiness. Western societies in particular have seen a mental health epidemic in the past few decades, focused primarily around depression and anxiety disorders.

There is a strong correlation between depressive symptoms and reduction in sexual activity and desire. Conducting a review of relevant studies for the Journal of Sexual Medicine, Evan Atlantis and Thomas Sullivan at the University of Adelaide found significant evidence that depression leads to increases in sexual dysfunction and reductions in sexual desire. Bringing this evidence together with the noted increases mental health issues, Twenge, Sherman and Wells argue there is a causal link between drops in happiness and average drops in sexual activity.

Research connects these mental health epidemics with the increasingly insecure nature of modern life, particularly for younger generations. It is this generation that has shown the highest drops in sexual activity, with research from Jean Twenge showing millennials are reporting having fewer sexual encounters than either Generation X or the baby boomers did at the same age. Job and housing insecurity, the fear of climate change, and the destruction of communal spaces and social life, have all been found to connect to mental health problems.