Lack of sleep can lead to weight gain due to slowed metabolism and increased appetite. It also increases stress levels and risk of anxiety or heart conditions by disrupting genes regulating stress. Poor sleep is linked to moodiness and depression in 50% of sufferers. It causes dehydrated, swollen skin under the eyes. Drowsy driving from fatigue leads to 5% of accidents due to slowed reaction and impaired judgment. Lack of sleep lowers body temperature and immunity, making people more prone to illness. It negatively impacts thinking ability and memory.