Sleep deprivation occurs when a person consistently gets less sleep than their body needs to function optimally. It can be acute — resulting from one or more nights of insufficient sleep — or chronic, developing over weeks or months of regularly shortened sleep. Both forms can have significant consequences for health, cognitive function, and overall wellbeing. The effects of sleep deprivation are wide-ranging and begin to appear after even one night of insufficient sleep. Short-term consequences include impaired concentration and memory, slowed reaction times, reduced decision-making ability, increased irritability and emotional reactivity, and heightened sensitivity to pain. The risk of accidents and errors — including traffic accidents — increases substantially with sleep deprivation. Chronic sleep deprivation has more serious long-term consequences. It is associated with an increased risk of obesity, as sleep deprivation disrupts the hormones that regulate hunger and appetite (ghrelin and leptin). It also increases the risk of type 2 diabetes, cardiovascular disease, high blood pressure, and impaired immune function, making the body more susceptible to infections. Mental health is also affected — chronic sleep deprivation is closely linked to depression, anxiety, and other mood disorders. The causes of sleep deprivation include voluntary restriction of sleep due to lifestyle choices or work demands, sleep disorders such as insomnia or sleep apnea, irregular work schedules, caregiving responsibilities, and environmental factors. Addressing sleep deprivation requires identifying and addressing its underlying cause. For most people, prioritizing adequate sleep time, maintaining a consistent sleep schedule, and addressing sleep-disrupting habits are the most effective approaches. If a sleep disorder is suspected, medical evaluation is recommended.