The common underlying causes of insomnia can be split into a number of categories.

Physical

Insomnia can be caused by an underlying physical condition causing involuntary movement, pain or discomfort. Examples include:

• restless leg syndrome,
• coughing,
• arthritis, headaches and back pain,
• hot flashes (due to the menopause),
• head injury,
• gastrointestinal disorders, e.g. GERD and ulcers,
• pruritus (excessive itching), and
• Parkinson's disease.

Physiological

Disruptions within the sleeping environment or to bedtime routines can cause insomnia. Factors include:

• noise,
• light,
• snoring,
• partner moving about,
• jet lag,
• activities before bedtime, like reading or exercise.

If you are a night or shift worker, your job can disturb your ability to sleep properly as your natural body clock will be affected. This is because your body is designed to release awake chemicals when there is daylight and sleepy chemicals when it gets dark.

Psychological

Loss or worry can make sleeping difficult, caused by events such as:

• bereavement,
• relationship problems,
• exam stress,
• work worries, and
• anxieties about being unable to sleep.

Psychiatric

Underlying mental health problems can affect your sleeping patterns, such as:

• depression,
• dementia, or
• anxiety

Pharmacological

Sleeping problems can result from the effects of medicines. Withdrawal from certain medicines such as hypnotics (prescribed for short-term insomnia) may cause re-bound insomnia, which means if you stop taking them, the sleeping problems can come back.

Taking other medicines can produce side effects reduce the quality of sleep, for example:

• alcohol,
• antidepressants,
• appetite suppressants,
• decongestants,
• thyroid hormones,
• beta-blockers and
• corticosteroids.

Sleep disorders can also affect you getting a good night's sleep including:

• Narcolepsy this condition causes extreme tiredness and you can fall asleep at any time of the day without being able to control it.
  
• Sleepwalking getting out of bed and moving around in your sleep, for example, walking, opening doors and climbing up and down stairs.
  
• Sleep apnea - a disorder in which you have irregular breathing at night and are extremely sleepy during the day.
  
• Sleep starts muscle jerks or a sensation of falling when you are just going off to sleep.