People with social anxiety disorder are, research shows, seven times more likely to develop a dependence on cannabis than the general population.  The link between social anxiety disorder and marijuana addiction is stronger than the link between cannabis dependence and any other mood disorder, and people with social phobia often find that their symptoms get worse, rather than better, once they start smoking pot .
Can both short-term and long-term use of weed lead to the symptoms of social phobia in people who were not already suffering from it, though? Anyone who has experienced social anxiety or the need to isolate themselves from others after using weed will already have their answer — but what does science say?
Social Phobia: A Brief Overview
Social anxiety disorder, also called social phobia, is characterized by a persistent, strong fear of certain social situations, especially those where one feels they may be embarrassed or humiliated. People with social phobia will either go to great lengths to avoid the situations that make them anxious, or will experience great anxiety if they endure them. Either way, the anxiety has a significant negative impact on the person's daily functioning. In order to qualify for a social anxiety disorder diagnosis, the anxiety has to be long-term, typically lasting at least six months. 
Social Anxiety While High
People who use marijuana recreationally will do so to experience the effects the drug is known for — a pleasant feeling of intoxication (feeling high), euphoria, feeling more relaxed, a better mood, and decreased anxiety. When used in friendly surroundings, weed users typically feel more sociable. Those who are already suffering from anxiety may even see smoking pot as one of the possible relaxation techniques for anxiety, which, considering weed's typical effects, makes sense.
Some users, however, react quite differently to smoking pot. Severe anxiety, panic, paranoia, and even psychosis are possible. These adverse reactions are more likely to strike weed users who smoked higher doses of marijuana and those who were already suffering from mental health issues — known to them or not. 
Weed users can additionally experience depersonalization, a phenomenon in which they feel detached from their bodies and perceive the world around them as less real and significant. 
Studies demonstrate that inexperienced marijuana users are more likely to experience severe anxiety after smoking pot than those who are already familiar with cannabis, 
In some cases, this can be attributed simply to being new to the drug or having smoked too much cannabis. In other cases, it is a sign that marijuana causes you adverse effects and you need to stay away from it. While you could say that weed led to a temporary social phobia in this case, we have already seen that diagnosible social anxiety disorder is a long term problem that leads to a significant negative impact on your daily life. You will not meet the diagnostic criteria if your symptoms wear off when you are no longer high — the "cure" for your symptoms is not medication or therapy, but quitting weed.
Social Anxiety After Long-Term Weed Use
Does long-term cannabis use have the ability to cause social anxiety disorder in people who were not suffering from this disorder before they began to use marijuana? Studies are divided on the topic. One study says, for instance, that cannabis use is associated with a slightly elevated risk of increased anxiety.  Another study found that 17 percent of frequent cannabis users meet the diagnostic criteria for an anxiety disorder, compared to five percent of the general population. 
Given the fact that we know that people with social anxiety disorder react differently to smoking weed than the general population , the latter certainly seems possible.
An abundance of research shows that people who meet the diagnostic criteria for social phobia are more likely to become addicted to marijuana [1,2]. We also know that some people experience acute anxiety and other adverse reactions, such as psychosis, depersonalization, panic, and paranoia. It is not yet clear whether weed use can lead to social anxiety all by itself, however.
Having said that, should you be experiencing symptoms of social anxiety disorder after using weed, it is best to commit to quitting cannabis. Long-term marijuana users may find this difficult, and outpatient treatment to help you through your withdrawal period may be warranted. 
People who genuinely believe that they have developed social phobia will want to look into ways to manage social interactions with social anxiety disorders and relaxation techniques for anxiety. This will be most effective if they seek professional help from a psychologist or psychiatrist.