I don&#x27;t know, but I found this to be the interesting bit:<p>&gt; Depressed and anxious people might simply be too good at learning about bad outcomes<p>&gt; Over the past few decades, researchers have been discussing that mental health issues such as depression and anxiety might fundamentally be disorders of learning, rather than outcomes of a ‘chemical imbalance’ that requires correction by a serotonin boost. Specifically, certain individuals which have atypical function of the serotonin system (which might be caused by genetic factors or stressful lives) may be at risk of developing depression or anxiety because they are too good at learning about negative outcomes, and thus are more likely to feel that the world is a bad place if they experience negative life events. One of the most talked-about studies in the psychiatric literature supports this possibility (6). It found that individuals with a particular genotype affecting the serotonin system were more likely than others to develop depression or anxiety only if they had experienced stressful life events, such as child abuse, unemployment, or loss of a loved one. Clearly, having an atypical serotonin system alone wasn’t enough – it had to be combined with negative experiences.