Effects of marijuana (THC) and other factors in inducing paranoia
Paranoia following THC consumption may occur due to illicit nature of marijuana, the possibility of paranoia-tendency people to consume THC, or the role of other factors instead of THC producing paranoia, such as by the cognitive model shown below.
There is actually very little research on THC and paranoia, the first experimental study being conducted only in 2015. Based on evidence, I would argue that the awareness of consuming THC is not the reason for paranoia - in fact, it showed to reduce paranoia. However, the study suggests that that THC does not directly induce paranoia, but introduces effects such as panic, anxiety, depression, and negativity, which in turn increase one’s likelihood for paranoia.
THC, however, has been studied in terms of paranoia-resembling psychotic effects it may induce. This could occur due to increased cortisol (known as the ‘stress hormone’) levels in the blood after consuming marijuana. It could also result from decreased dopamine (a neurotransmitter known for its pleasure-inducing effects) synthesis in those consuming THC.
This is a difficult topic to research, because several factors may induce paranoia
The possible reason for a lack of clarity regarding THC's link to paranoia is that it only affects some people; this may occur because factors such as environment and legality of the substance contribute to one’s likelihood of becoming paranoid.
However, there may also be neurotransmitter imbalances: For example, decreased levels of serotonin (another pleasure-inducing neurotransmitter) may make one more susceptible to depression, which can eventually lead to paranoia. Increased levels of dopamine have also been linked to paranoia.
Brain regional activity can also contribute to risk of developing paranoia: For example, elevated activation of the amygdala (contributes to emotion) can raise paranoia.
Genetic differences may also contribute; it has been shown that people with a shorter allele for the serotonin transporter (5-HT) gene were more likely to develop depression after a stressful event - again, a risk factor for paranoia.
In all, THC and paranoia is a long-winded link that will require meticulous controlling of confounding variables in order to conclusively outline any causal relationship. However, evidence is there, which adds to the multitudinous reasons not to consume marijuana in the first place.