Insomnia is the perception of inadequate or poor-quality sleep. It can be manifested by symptoms such as –difficulty in falling asleep, early wakening, waking frequently during the night, poor quality of sleep, or a combination of these. Insomnia may be classified by how long the symptoms are present. Temporary insomnia (transient insomnia) usually is due to situational changes, such as travel and stressful events. It lasts for less than a week or until the stressful event is resolved. Short-term insomnia lasts for 1-3 weeks, and long-term insomnia (chronic insomnia) continues for more than 3 weeks. Insomnia may also be classified as primary or secondary. Primary insomnia occurs in the absence of other medical problems, while secondary insomnia occurs as a result of a medical condition such as heart disease, arthritis, cancer, or heartburn causing wakefulness. Persons without adequate sleep can experience tiredness, lack of energy, and concentration problems; which they may attempt to overcome by excessive caffeine intake or nicotine use.