Depression is characterized by persistent feeling of depressed mood (feeling sad, empty, irritable), loss of interest in activities for most of the time of the day and easy fatigability..
Sleep disorders refer to conditions that disturb normal sleep pattern. They may range from insomnia to parasomnia to hypersomnia. Symptoms of sleep disorders include.
It refers to abuse of drugs that continues even when significant problems arise owing to the use. These problems may be both physical as well as psychological.