Hello, Depression is due to chemical imbalance in brain itself, so, they are interlinked and not different. Your symptoms reflect depression as, you mentioned being sad, lethargic, irritable, increased sleep but no quality or freshness after sleeping, having reduced interaction. There are certain other features which I will mention and see if you have them then -you should seek an appointment with a psychiatrist and get well. The other main features of depressive disorder are- lack of energy, lack of interst in previously pleasurable activities (like playing, watching tV, listening music, etc.) they can differently with different people. The feeling of hopelessness, helplessness and worthlessness may also come up from time to time, with ideas of doing self harm ( which means early intervention is a must). if you have first three of these even in some proportions, then it is likely to be depression and you will benefit immensely from treatment. Please ask more questions for clarification. Dr. Manisha Gopal MD neuropsychiatry