hi..thanks for the query. it is indeed disconcerting to see behavioural changes in a previously healthy child. We need to rule out several things here, first whether this is a stress reaction to a broken romantic relationship, or whether this stress of breakup has resulted in syndromal depressive episode characterised by low mood, lack of pleasure in routine & previously pleasurable activities, low self confidence, feeling of worthlessness, hopelessness, ideas of suicide & suicidal gestures or attempts (arm cutting in his case). Or this may be start of syndrome of Psychosis/schizophrenia. Lastly this may be also because of use of drugs like cannabis (easily available & relatively cheap) How is his academic performance of late? does he take interest in conversing, going out, socializing etc. with family & friends? Our first task is striking a rapport with him to understand his ongoing thought process, once he is comfortable to talk, we should take him to a Psychiatrist for detailed evaluation & then proceed with treatment accordingly. if need additional help, do revert to me. good luck