Psychological: The most common psychological problems include anxiety, stress, and depression. In fact, insomnia may be an indicator of depression. Many people will have insomnia during the more severe phases of a mental illness (such as in mania of bipolar disorder). Mania causes the excessive release of neurochemicals such as dopamine. Feelings of grief, depression or major depression, worry, anxiety or stress, exhilaration or excitement all may cause insomnia, either acute or chronic, depending upon the individual.

Physiological: Medical conditions can cause insomnia, such as chronic (long-term) pain (including arthritis, fibromyalgia, cancer), enlarged prostate, cystitis (common in women), over-active thyroid glands, congestive heart failure (CHF), gastroesophageal reflux disease (GERD, heartburn), chronic obstructive pulmonary disease (COPD), gastrointestinal disorders such as diarrhea, ulcers, or irritable bowel syndrome (IBS), and nervous system diseases, such as Alzheimer's disease or Parkinson's disease. These conditions cause imbalances and changes in circadian rhythm (24 hour light and dark balance) and sleep/wake balance.

Medications: Certain prescription and non-prescription medications may also cause acute or chronic (long-term) insomnia. If the insomnia is related to a medication side effect, a normal sleep/wake pattern should be achieved shortly after discontinuing the medication. Medicines that stimulate brain neurochemistry may cause insomnia. These include nasal decongestants, weight loss drugs, amphetamines (including methamphetamine or crystal meth), some antidepressants, cocaine, and some asthma and heart medications. Caffeine, alcohol, and nicotine may also contribute to insomnia by altering brain chemistry, thereby disrupting the normal sleep/wake cycle. The abrupt discontinuation of alcohol (in alcoholics) can also contribute to insomnia. The abrupt stopping of medications (such as sleeping pills, hypnotics, anti-anxiety drugs, and antidepressants) can cause acute insomnia.

Sleep apnea: Sleep apnea may also cause insomnia. Sleep apnea means cessation of breath, and is characterized by repetitive episodes of upper airway obstruction (mouth, nose, throat) that occur during sleep, usually associated with a reduction in blood oxygen saturation. Airway muscles relax and collapse when asleep, causing them to become obstructed (blocked) at several possible sites, resulting in snoring. The upper airway can be obstructed by excess tissue in the airway, such as large adenoids (tonsils) or a large tongue. Another site of obstruction can be the nasal passages. Sleep apnea can be a serious condition, and can result in excessive daytime sleepiness, loud snoring, morning headaches, hypertension (high blood pressure), weight gain, irritability and personality changes, depression, difficulty concentrating, excessive perspiring during sleep, heartburn, reduced libido (sexual drive), nocturia (frequent urination at night), restless sleep, and snorting, gasping, or choking.

Other common causes: A disruptive bed partner with loud snoring or periodic leg movements (restless leg syndrome or RLS) may also cause insomnia. Nocturnal polyuria, or excessive nighttime urination, can be very disturbing to sleep. Excessive thirst or the use of diuretics can also cause these symptoms. Not getting enough light during the day can cause the natural circadian rhythm and the sleep/wake cycle to be disturbed, causing insomnia. Jet lag, shift work, wake-sleep pattern disturbances, bed or bedroom not conducive to sleep, aging, excessive sleep during the day, and excessive physical or intellectual stimulation at bedtime can all contribute to acute or chronic insomnia.

Causes in infants: Most newborn babies wake several times during the night, but by the age of six months they typically sleep through the night. At one year, babies will sleep an average of about 16 hours in every 24. Two to three hours of this sleep will be during the day. Causes of sleeplessness in infants may include a desire for parental attention, infantile colic or other digestive problems such as indigestion, hunger, teething, and fever or other illness such as a cold or influenza.

Medical history: A doctor will ask the individual experiencing insomnia questions to evaluate the medical history. Questions investigate mental health problems, medications (supplements, prescription and non-prescription), history of pain, leisure habits, work and home situation, and others.

Sleep history: The doctor will also inquire about the individual's sleep history. Questions inquire about length and severity of the sleeping problem, routines before sleeping, snoring, and noise levels.

Physical exam: The doctor will also give the individual a full physical exam, including blood tests for conditions that may interfere with sleep including thyroid problems.

Sleep study (Polysomnogram): A polysomnogram is a recording of the breathing, movements, heart function, and brain activity during sleep. For this study, the individual sleeps overnight at a sleep center or hospital. A sleep study will be recommended if there are signs of sleep apnea or restless legs syndrome (RLS).

Other: The Epworth Sleepiness Scale is an example of a validated questionnaire that can be used to assess daytime sleepiness. It asks questions about the chances of dozing off during various daily functions such as watching TV, sitting and reading, or driving a car. Actigraphy is another technique to assess sleep-wake patterns over time. Actigraphs are small, wrist-worn devices (about the size of a wristwatch) that measure movement. They contain a microprocessor and on-board memory and can provide objective data on daytime activity. Actigraphs measure day-to-day activity of an individual, recording movement being made during waking and sleeping hours along with light, sound, and temperature. Actigraphy is useful for assessing daytime sleepiness in situations where a laboratory sleep latency test is not appropriate. Actigraphy is used to clinically evaluate insomnia, circadian rhythm sleep disorders, excessive sleepiness, and restless leg syndrome. It is also used in the assessing of the effectiveness of treatments for these disorders.

The main signs and symptoms of insomnia are trouble getting, staying asleep, or waking early, followed by a distinct feeling of fatigue (tiredness) the following day. Most often, daytime symptoms will bring people to seek medical attention. Daytime problems caused by insomnia include anxiousness, irritability, fatigue (tiredness), poor concentration and focus, difficulty with memory, impaired motor coordination, irritability and impaired social interaction, and motor vehicle accidents because of fatigued, sleep-deprived drivers.

Whatever the reason for sleep loss, insomnia can affect people both mentally and physically. The impact can build up over time.

People with chronic insomnia are more likely than others to develop psychiatric problems, such as depression or an anxiety disorder. Additionally, lack of sleep slows problem-solving skills. Long-term sleep deprivation may be due to conditions such as sleep apnea, which increase the severity of chronic diseases (including high blood pressure and diabetes).

Insufficient sleep can also lead to serious or even fatal accidents. According to the National Highway Traffic Safety Administration, more than 100,000 crashes each year are due to drivers falling asleep at the wheel.

In a recent study, scientists discovered that youngsters who snore nightly scored significantly lower on vocabulary tests than those who snore less often.

Risk factors associated with developing insomnia include stress, depression, pregnancy, menopause, having frequent, major shifts in work hours, and traveling long distances with time changes (jet lag). Stimulant drinks containing caffeine may increase the risk of developing insomnia, as do certain prescription and non-prescription medications, including nasal decongestants (including pseudoephedrine or Sudafed®), weight loss drugs (including phentermine and sibutramine), amphetamines, and some antidepressants (including bupropion or Wellbutrin®), asthma (including albuterol or Ventolin®), and blood pressure medications (including beta blockers).