My parents are both depressed?

They have been for a while and its starting to get to me. My dad is a workaholic who can never escape his job and my mom has been clinically depressed since I was born. She sometimes confides her suicide thoughts with me and it scares me, even though I know (hope?) she would never act on them. I know it sounds insensitive but I can't stand it. I am the only one who was ever happy and now I'm getting tire of always having to hold things together. No one in my house will even talk to me unless I act them direct unavoidable questions. I AM GOING INSANE! How can I help them? My mom already sees a therapist and is on drugs and stuff and I can't convince my dad to work less even though I try every single night. I feel like there is nothing I can do. Is there?