ANSWER: Depression
EXPLANATION: Ivan is showing signs of Depression. He may have affected by something or by some event due to which his behavior has changed significantly and he started having an addiction towards alcohol. The signs of depression often shows that the person will have depressed mood, feeling of guilt and restlessness. Ivan have a guilt feeling when he consumes alcohol which is why he abuses it but also feels restless and depressed if he does not consume that. He thinks that alcohol is the solution to his depression which is why he feels normal after consuming it.
