A number of people with mental illnesses experience dissociative disorder: a disturbance of thinking, awareness, identity, consciousness or memory. Dissociation is more severe than just ordinary forgetfulness and is also not associated with any underlying cause of memory deficits or altered consciousness (e.g., neurological illnesses, substance or alcohol abuse). Some people have dissociative events that last only moments whereas others experience extended periods of dissociation. There is an association between traumatic events and the process of dissociation. It may be that dissociation is a way the mind/brain contends with overwhelming stimuli.