Sleeplessness An immediate psychological effect of scary movies on the minds of people is lack of sleep. The person may be unable to sleep through the night for few days, even months after watching the movie. He/she may need to use a nightlight while sleeping. The thoughts of the horrifying characters of the horror movie and the situations may haunt him/her, leading to sleepless nights. This condition last for a week to even a year. People tend to develop Insomnia and nightmares; though insomnia might be harmless, repeated occurrence of nightmares might lead to chronic insomnia which in turn affects the mental and physical health.