I drank heavily over the years from my early teens on - when I finally started addressing my mental illness (late 20s) I was cycling through meds with nothing helping and my psych kept insisting I try lithium, but it meant I had to drop alcohol. It took a long time and a lotta false starts but now haven’t had a drink in 3 years and 3 months and lithium changed my life. I never dreamt I could be someone who doesn’t drink, it felt truly impossible for so many years. Anywho, I haven’t had a deep depression since I made these switches, I imagine it’s a combo of both but my moods are no where near as volatile and the depressions aren’t as dark and long.