Attributing drinking to depression, genetics, medication, or disease is attractive to the drunk because 1) it lifts a huge burden off their shoulders giving them an externally based excuse for their behavior choices, and 2) in current culture these are socially acceptable excuses believed by most people.
The ugly truth is that there is one and only one reason drinkers ever drink: for the temporary pleasure it brings. Any other explanation is simply an excuse, a sales pitch. The excuses used vary depending on what works.
True or not these excuses are not helpful to the drunk or to the people in their lives who buy them. Over drinking should always be framed as what it is: a selfish choice. Drinking is not a medical treatment for depression. In fact it causes depression, which the drunk then uses as another excuse to continue. This is not a helpful mind virus to keep in your head.