There is no one answer to this question as everyone's mental health is affected by different things. However, there is some evidence to suggest that being a vegetarian can affect mental health. For example, one study found that vegetarians are more likely to suffer from depression than non-vegetarians. Another study found that vegetarianism is associated with a higher risk of anxiety and OCD.
So, if you are considering becoming a vegetarian, it is important to be aware of the potential mental health risks. However, it is also important to remember that everyone is different and not everyone will experience mental health problems as a result of becoming a vegetarian.