system
Given the following post, respond as if you're commenting on Reddit:
human
What are other theories of the cause/s of depression other than serotonin imbalance?

Are any viewed more highly than others? The recent study on serotonin got me wondering about causes of depression.
gpt
Well for one thing, anhedonia (an inability to experience pleasure/reward) is increasingly seen as a core feature of depression, and depends at least partly on a dopamine deficiency rather than serotonin. That doesn't mean a dopamine deficiency **causes** depression though. 

More broadly for depression as a whole, chronic stress has been implicated in depression for a good while, with stress-related overactivation of glucocorticoid and/or mineralocorticoid receptors by cortisol and other stress hormones in several areas of the brain being implicated as potential mechanisms, via atrophy of said brain areas after exposure to chronic stress (a notable area being the hippocampus, itself increasingly implicated in depression). Obviously any other mental health problems or disabilities that might increase chronic stress, like anxiety, psychotic disorders, neurodevelopmental disorders, etc., could all increase risk for depression via this pathway. 

These are the more biological/neuropharmacological explanations but hopefully others will fill in on some of the social ones, for instance increased social isolation and sedentary lifestyles in recent decades, both of which deprive us of protective factors which would otherwise buffer against a range of poor health outcomes including depression.