Hi, Slabasdas, welcome to PsychCentral (PC).

Psychiatrists are medical doctors who have specialized in psychiatry; they can prescribe medicine but usually do not do psychotherapy. An assessment/diagnosis would be made by the person treating you, might vary depending on the person you chose and there orientation.

A therapist works over time with you to help you change or manage thoughts, feelings, and behaviors. They run the gamit between counsellors, social workers, psychologists, and, sometimes, psychiatrists.

Were I you, I would pick one of the three conditions you know you have; depression, or anxiety, or drug abuse, and decide how you wanted to proceed for that one problem that bothers you the most.

I would choose drug abuse and get clear of that monkey on your back as it can exacerbate the other two. Your reasons for drug abuse probably contain problems with the other two and working on that behavior could help with the other two. Drug treatment is likely to be a bit less expensive than a psychiatrist or therapist also as it is a behavior and treatment is less likely to be as complicated as it could be for the others. Success in a behavior arena would give you some self confidence that you could succeed in treatment and also might give you more of an idea how treatment operates and who the players are and maybe give you some references for further treatment that you would already know and trust.