My friend says anxiety disorder affect my teeth. Is it true?

Possibly. Some people with anxiety grind their teeth. This can wear them down.
Yes and no. Only if it makes you do things pertaining to your teeth. This couyld include grinding.
Anxiety and teeth. There are a couple of things that can effect your teeth. First, many patients with anxiety will grind or clench their teeth and this can be very destructive. Second, many of the anti anxiety medication can cause a dry mouth. This can also be destructive by increasing dental decay, cavities. Your dentist will help, you keep your mouth healthy.
No. There is actually no evidence that anxiety itself affects your teeth from grinding a lot. Some people do suffer from teeth grinding called bruxism, but it is not really related to a person's level of anxiety.
Yes. Many people with anxiety disorder grind their teeth without realizing it, which can lead to jaw pain, and can cause excessive wear on the teeth, making them more suceptable to dental disease.