A drug addict is likely to show some of these symptoms, however, symptoms will change depending upon the drug being used: -- Excessive/very little sleep and appetite.- Unexplained mood swings.- Suspicious and odd behaviour such as avoiding family members, becoming secretive, locking doors.- Restlessness, making excuses to go out everyday at particular times.- Appearing drowsy, dull, lost in his world.- Cramps in the abdomen or legs, diarrhoea, or constipation. When these mentioned symptoms increase in frequency, duration and intensity, a professional medical help is to be sought.