You could be, there's growing evidence that early-onset cannabis use can affect the brain's development negatively. You're at a critical age in your brain's development, which extends into your early 20s, so any regular substance use will absolutely have a lasting (if not permanent) effect on your brain's structure and function.
A good summary of the evidence-based knowledge by the Canadian Psychiatric Association:
• The human brain undergoes a maturational process
during adolescence that includes reorganization,
refinements and functional improvements. This is
driven by changes in brain grey matter (GM) due
to synaptic pruning (elimination of underutilized or
unnecessary neural connections), and white matter
(WM) due to myelination.
• These changes continue at least until the mid-20s and
thus brain maturation is vulnerable during this time
to stressors/insults.
• The endocannabinoid system plays a role in this
brain maturation and thus exogenous cannabinoids
from cannabis can affect this process directly in a
negative way.
• Regular cannabis use in youth and young adults
can affect aspects of cognition, including attention,
memory, processing speed, visuospatial functioning
and overall intelligence. Worse performance is
related to earlier adolescent onset of use. Abstinence
following regular use may improve some, but not all,
of these cognitive domains.
• Early and regular use increases the risk of developing
a primary psychotic illness in those individuals who
are vulnerable. Vulnerability factors are not currently
clear, but may include factors such as childhood
trauma and genetics. In those young adults who have
developed psychosis, continued cannabis use worsens
long-term symptom and functional outcomes.
• Cannabis may increase the risk of depression and
early regular use is associated with younger age
of onset of symptoms of psychosis and of bipolar
disorder.
• Cannabis with high tetrahydrocannabinol (THC)
content (high potency) can result in significantly
worse mental health and cognitive outcomes,
including worsening of panic disorder and other
anxiety disorders.
• Early age of use of cannabis increases the potential
for adult dependence to cannabis.
• Cannabis may be associated with increased
progression to other illicit drug use in the context of
particular factors (e.g., high frequency and early age
of use).
http://www.cpa-apc.org/wp-content/u...sition-Statement-ENG-FINAL-no-footers-web.pdf
Also this one's a bit dense but a good review of the literature on the topic:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3930618/
As alluring as drugs may be, you're really much better off waiting until your brain has fully developed before you start experimenting.
If you start having a weekly cigarette at your age (or any age really) you will most likely become addicted, one of the most addictive drugs there is, many people simply can't quit, and it kills them.
Look after yourself
