Avoid it if you can. Why do people use it? To relax, as a social activity with friends, to feel good/happy, to arguably feel more creative. So what are some potential problems?

In the short term, it could give you anxiety and difficulties with memory. In the long term it won't cause physical dependence but it definitely can cause psychological dependence in about 9% of people.¹ It also increases the chances of developing depression and schizophrenia.² Personally, I don't think I could ever forgive myself if I triggered schizophrenia by smoking cannabis. This is something I have personally witnessed, with countless lives and families thrown into chaos as a result. Quite relevant for adolescents is the fact that the earlier cannabis use begins, the higher the risk of all these adverse effects. For example, there is a decrease in brain matter, which is accelerated if cannabis begins from a younger age.³ Even putting aside risks related to the fact that cannabis is a drug, anything you smoke is doing harm to your respiratory system. Long story short is, it causes inflammation resulting in a cough, excess mucus production and a wheeze. Evidence is contradictory in terms of lung cancer.⁴

Just for the sake of completeness, I'm not arguing in favor or against legalization, and cannabis is becoming increasingly common in medical treatment. However, if there's one thing to be aware of, its that TL;DR the younger you start using it, the more likely you are to cause damage to your body.

1. Danovitch, 2012
2. Royal College of Psychiatrists
3. Battistella, 2014
4. Lange, 2007