Need guidance for my son's mental health

Dear Sirs, I would like your guidance on this matter. My son approached me and said that he hasn't been feeling normal for some while. He says that he feels that he is unable to concentrate and remember things as well as he used to. He also mentioned that on certain days he feels he has hardly any energy and finds it difficult to perform simple tasks. I have noticed that he has frequent mood swings and gets very angry at himself quite frequently. When he was younger he used to be a lot more motivated and happier than he seems currently. His academic record has also gone down suddenly. He has become very unstable emotionally. I would like to know whether he has some mental health problem and can depression be a cause for this. I eagerly await your response. Thanking you.