Some symptoms which can be experienced by addicted person himself/herself are:
i. Tolerance increases that’s why needs to engage in addictive substance becomes more and more to get desired effect.
ii. Withdrawal happens when the person doesn’t take the addicted substance or engage in addicted behaviour (like gambling). Thus, experience unpleasant symptoms.
iii. It becomes difficult in cutting down or controlling the addicted behaviour or substance.
iv. Social, occupational and recreational activities gets hampered.
v. Addicted person spends most of his/her time in thinking and planning about getting addicted substances (like drugs, alcohol, cigarettes, etc). He/she spends all his/her money to buy such substances even by lying, thieving, selling his/her own properties or being criminal.
Some common signs which can be observed in addicted person by other people are:
i. Extreme changes in mood occur in short time. Like being sometime really happy, sometime really sad, sometime anxious, sometime exited and so on. But these types of mood change are also common in non-addicted teenagers. As teenage is the period of stress.
ii. Sleeping more or less than usual or sleeping at different times of day or night.
iii. Unexpectedly changes in energy. So addicted person sometimes feels extremely tired or sometimes feels extremely energetic.
iv. Unexpected weight loss or weight gain.
v. Secretiveness and lying behaviour are seen.
vi. Stealing behaviour can also be seen.
vii. Addicted person sometimes holds a large amounts of money and sometimes don’t bear any money.
viii. Changes in social groups and new or unusual friends can be observed.
ix. Repeatedly going outside without explaining, often with a sense of urgency.
x. Drugs or other addictive substance being stashed can be seen with addicted person.
xi. Problems at school, frequently missing school, sudden disinterest in study or sudden drop in grade.
Above given are just signs and symptoms of addictions. Sometimes some of above mentioned signs can also be seen in non-addicted person due to various reasons. So, don’t jump into conclusion and blame someone of addiction but keep a little distance with such person. Before blaming other be sure and have strong evidence and don’t forget to take the opinion of the person about this matter if you think he/she is addict.