All psychoactive substances have the capacity to change someone's personality, either for the duration of when it in their system, or by the experiences that happen while the person is under the influence. Environment and gene expression can be multidimensional, meaning that if you're in an place that triggers stress, which can trigger a gene that you may have but is not expressed (such as schizophrenia), then perhaps there will be a permanent alteration of your personality. Psychoactive substances can also do this.
Magic mushrooms can change someone's personality. These are psychedelic, which cause hallucinations. It is so powerful that these have been known to cause flashbacks years after someone has taken them. These drugs cause a change in mood, perception and behavior. A bad trip can certainly change someone personality without him or her knowing it.
Drugs are extremely powerful, whether they are natural or made in a lab. They can be mind-altering, physical impairing, and in the case of "magic mushrooms", personality-changing. Hallucinogens make people see things that do not exist, or see things that do exist in strange ways. This can cause them to react to things completely differently than they would if they were not influenced by the drug.
At sixty four years old and having used psychedelics throughout my late teens and early twenties I'm still waiting for that free flashback. I really doubt there coming but that's only my opinion. I actually grew out of my experimental years, graduated college with honors and became, by any standard, well balanced emotionally and financially successful. Just my thoughts and opinion, be safe.
Some people claim that these bald-head mushrooms are magical. There are about 100 different species around. They contain compounds which cause hallucinations and euphoria. They used to be used in religious ceremonies in Central America. The mushrooms will not change your personality; however, they will likely make you feel different if not allergic. In the short-term, you may feel less fearful or less emotional. But then you'll go back to the way you were. People should just stay away from these mushrooms.