I found this to be the case. Tried Sertraline for a while, gave me headaches and made me feel sick. Then as part of a new gym plan, started taking Omega 3+VitD daily, and I just felt a sense of calm and peace after a few weeks. The massive uptick in exercise probably also helped. I also felt quite an extreme uptick because I was a vegan for 10 years, and found out I had basically zero Omega 3 in my blood. I suspect one of the main reasons my mental health declined was due to the lack of Omega 3.
Disclaimer, not saying vegans should stop being vegans, just make sure you find a good supplement, and make sure you understand the difference between EPA/DHA Omega 3.
Disclaimer, not saying vegans should stop being vegans, just make sure you find a good supplement, and make sure you understand the difference between EPA/DHA Omega 3.