Depression, mood swings. To go for?

Hello Dr, I have a concern one of my family members have been facing the problem of depression since school time and at that time the person had to take medication. Since then he has frequent mood swings from too much of excitement to ample depression that I had to council him for days to recover then when he is normal he is just too good at times but then at times too aggressive and angry. Also he fears from taking challenges in life and unknowingly he had been bullied and dominated in childhood in relatives and social circles. His personal life and family life is suffering and also his career. I find the symptoms similar to Bipolar disorder but I know when we talk about mental health then there are situations where there are similarity between two common diseases as their symptoms are similar but the treatment is surely not for eg- Autism and ADHD. I am not able to understand:- whom to consult or visit? what treatment to go for? Who can help find that what exactly is happeni