1/ depends what you call a disease
2/ yes
By that I don't mean in the simple sense that if you have two alcoholic parents you *will be* an alcoholic but you will have a higher chance of becoming one.
Classic experiment:
A large group of mice had there water replaced with ethanol solution. After a while water feeders were reintroduced with them.
Most mice went back to water but some preferred the "mouse vodka"
The groups were split up and cross bred and the experiment repeated.
The alcohol preferring mice had a much higher proportion of off spring that too preferred alcohol.
Other work also pointing to this details here:
http://209.180.175.75/becalmd/alcohol.htm
Unfortunately a lot of people come to this question with baggage - they want to believe that it's "poor moral fibre" because a genetic componant is seen as an "excuse"
The other baggage is that people often don't like the idea that our free will is in some way compromised.
The idea that many of our personality traits - such as tendency to take risks or how happy we are - could be inherited is totally at odds with the way they see the world