If you begin to notice unexplained changes in physical appearance or unusual behavior, this may be a sign of substance use—or perhaps a sign of another unidentified problem. 
            To definitively know requires a professional who will conduct  a screening. Still, it is better to be aware of signs rather than live in denial. So care enough to take assessment. Here are some of the signs.
            
              - 
                Denying use; lying and covering up 
- 
                Sense that the person will "do anything" to use again regardless of consequences 
- 
                Loss of control or choice of use (drug-seeking behavior) 
- 
                Loss of interest in previously enjoyed activities 
- 
                Emotional instability 
- 
                Hyperactive or hyper-aggressive 
- 
                Depression, sadness, isolation 
- 
                Missing school or work 
- 
                Failure to fulfill responsibilities at home, school or work 
- 
                Complaints from teachers or co-workers 
- 
                Reports of intoxication at school or work 
- 
                Secretive behavior 
- 
                Avoiding eye contact 
- 
                Locked doors 
- 
                Going out every night 
- 
                Change in friends or peer group 
- 
                Change in clothing or appearance 
- 
                Unusual smells on clothing or breath 
- 
                Heavy use of over-the-counter preparations to reduce eye reddening, nasal irritation, or bad breath 
- 
                Hidden stashes of alcohol 
- 
                Alcohol missing from your supply 
- 
                Prescription medicine missing 
- 
                Visiting on-line pharmacy internet sites 
- 
                Money missing 
- 
                Valuables missing 
- 
                Disappearances for long periods of time 
- 
                Running away 
- 
                Secretive phone calls 
- 
                Unusual containers or wrappers