Honestly I think it’s most likely that you’re simply overworked. (many/most people are)

I think that being overworked, together with emotional instability/lack of security, are the most prevalent causes of mental illnesses in our society today. It’s no “chemical imbalance in your brain” story. Sure, there’s chemical imbalance, but where does that imbalance come from? I guess it’s mostly that our bodies aren’t built for today’s demands.