Re: depression, has practicing Aikido helped in any way?
First part: any physical activity can help. Anecdote: it's helped me. It's also helped my social anxiety.
Second part: Never stop taking, or adjust how/when you take, any medication without consulting your doctor. I would think it's unethical to not take a necessary medication as it shows you don't respect yourself enough to accept healing.
Keep training and have fun!