Please get blood tests done to check for vitamin D, B12 and iron (anemia) deficiencies and thyroid. Have bad personal experience with first two which can cause too much fatigue and lead to body pain, insomnia and moodiness/depression.
Exercise is very important for both improving health and mood. Make him exercise for at least half hour a day. Would suggest sit ups, plank and push ups which strengthen the body. Can start with 10 and slowly increase daily. Can do at night and then take bath which will help with sleep as well.
Chanting is a great way to keep negative thoughts at bay and also bring positivity. Can pick a favorite God and slogam they feel good about for chanting. Can fix a time period for the improvement (say an year) and கோவிலுக்கு வேண்டுதல் வைக்கலாம். அவர் சீக்கிரம் நலம் அடைந்து குடும்பத்தில் மகிழ்ச்சி திரும்ப வாழ்த்துகள்