Regardless, it's a feedback loop. People who deal with depression/anxiety are more likely to develop drug addictions. A "normal" person can usually try a given drug once and be fine. Someone with a predisposition to addiction can't do the same.
Likewise a lot of people can casually use porn without much of an issue, but some people allow their consumption to develop into an addiction that negatively impact their life.
1. Do you find yourself craving it?
2. Do you continually feel the need to increase your intake? (i.e. developing a tolerance)
3. Would you be embarrassed if a like-minded friend knew about your habit?
4. If you were suddenly cut off from it for a few days, how would it make you feel?
[0] - natural like how we crave sugar for our health, yet harmful like I eat candy all day