The cause for bruxism is unknown. Factors that may contribute to teeth grinding include stress, facial or oral trauma, nervous system malfunction, poor diet, and allergies. Alcohol and drug use also increase the occurrence of bruxism.

Children with bruxism usually stop grinding their teeth before adulthood. However, bruxism can affect adults for an indefinite period of time. Adults with bruxism have increased occurrence of grinding during times of stress (e.g., health-related, family-related, or job-related).

Although teeth grinding can be caused by stress and anxiety, it often occurs during sleep and is more likely caused by an abnormal bite or missing or crooked teeth.