What is the main cause of insomnia?

The main causes of insomnia would be

Stress

Stress can have many sources, like the death or illness of someone you love, divorce, problems at work or school, losing your job, concerns about your health or family, economic problems, unsatisfactory sex life

Anxiety

All kinds of everyday anxieties and even more serious anxiety disorders can keep you from sleeping

Depression

Depression can work two ways, or you sleep too much or you have a hard time catching some serious sleep. Waking up too early and not being able to go back to sleep is a schoolbook symptom of depression

Some other possible causes of insomnia

Medications

All kinds of prescription drugs can hold you back from a good night's sleep

Caffeine, alcohol and nicotine

Drinks like coffee, tea, cola, other caffeinated drinks and alcohol can cause insomnia

Hormonal changes

Women suffer from this when they have a hormonal shift just before menstruation and during menopause. In pregnant women this hormonal shift is one of the insomnia causes

Medical conditions

Frequent urinating, chronic pain or breathing difficulties can also lead to insomnia

Shift changes

Working shifts and especially rotating early and late shifts can seriously disrupt your circadian rhythm or internal clock, which could lead to sleeping difficulties

Change in environment

(Long distance) travel does the same thing in the form of a jet lag or simply the change in environment keeps you from catching sleep

Poor sleep hygiene

"Sleep hygiene" is a group of habits that can normally help you to have a good night's rest. Poor sleep hygiene on the other hand prevents this. This includes too much stimulating activities before you go to bed, or too much distractions. Also only use your bed what it is made for: sleep or sex

"Learned" insomnia

When you try too hard to fall asleep and start concentrating and worrying a bit too much about not being able to sleep you might just achieve exactly that…not falling asleep. Sort of a self fulfilling prophecy

Late night food

A light snack before you go to bed is perfectly OK, but eating too much may make you feel physically uncomfortable when you lie down in bed

Age

When you're older than 60 the changing sleep patterns over the years may cause the increase of insomnia. Almost 50% of all older people suffer from insomnia

High altitude

Some people suffer from insomnia because of the high altitude like in mountains

Withdrawal

People who are in a withdrawal process from alcohol, drugs, sedatives or other stimulants can also experience insomnia

Obstructive sleep apnea

People with obstructive sleep apnea can keep themselves or their bed partner from a decent night's rest