Short-term insomnia lasts for three weeks or less. Short-term insomnia and transient insomnia are almost similar in their causes.

Female hormonal changes can affect sleep patterns. One of the female hormones, progesterone, promotes sleep. During menstruation, when its levels are low, women may experience insomnia. On the other hand, during ovulation, the increase in progesterone levels increases sleepiness.

Fluctuations in the level of progesterone during pregnancy and menopause cause altered sleeping patterns leading to transient insomnia. Although women after 50 also experience chronic insomnia, this is usually caused by psychological or emotional factors.

Changes in working conditions, such as shifting schedules, also cause short-term insomnia. Also, people who tend to overwork get less sleep than the average. In one study, insomnia was also observed in people doing much computer work.

Light can also affect one's sleep. Too much light at night can disrupt sleep or even prevent sleepiness. Likewise, less light during the day, as in disabled or elderly patients who rarely go out can also cause short-term insomnia. This is because the levels of melatonin responding to darkness.

Melatonin is a hormone secreted by the pineal gland, a pea-sized gland at the center of the brain, that help regulate the cycles of sleeping and waking up.