It's hard to sort out. Because, parents generally do the best that they can do, and even abusive parents are like that for a reason. They might have been abused themselves (most abusers were victims of abuse even though it doesn't go the other way around), and might not have learned any better ways to parent, to discipline, to communicate strong feelings, etc. If they drink, there's a reason for it, like not knowing how to cope. If they say mean things (that's abuse too and hurts as much as physical abuse), they probably have some deep hurt inside somewhere that they never knew how to deal with. Bipolar disorder is possible when someone drinks a lot. Some people who are bipolar drink to self-medicate out of control emotions. It tends to mask the symptoms and often avoid being diagnosed and treated, but as you can see the side-effects are awful.

Whatever the reasons are, it doesn't change that you were hurt by someone you needed to love and cherish and protect you. How could that not have an effect on you? The reasons for their behavior don't change your need for healing and to make sense of it and to have your depression treated. Understanding can eventually make it more possible to move on and let go and make changes in your life in your own best interest. But that usually comes later.