"Insomnia" is a symptom, not a stand-alone diagnosis or a disease.
By definition, insomnia is "difficulty initiating or maintaining sleep, or both" or the observation of poor value sleep.
Not everyone agrees on one explanation, but in general:

• transient insomnia are classified as lasting less than one week
• short-term insomnia are classified as lasting between one to three weeks
• chronic insomnia are classified as lasting longer than three weeks

Insomnia is not defined by a specific number of hours of sleep that one gets.
Insomnia is generally classified based on the duration of the problem.
Although the nature of this association is unknown, people who experienced sleep insomnia says: "depression or anxiety was significantly more likely to develop insomnia".
Symptoms of Insomnia:

• Having a lot of time go to sleep (over 30 to 45 minutes)
• Getting out of bed many times every night
• Stumbling out of bed early and being incapable to return to sleep
• Awakening feeling tired or not rested well
• Having trouble to paying attention on tasks
• Feeling grumble, sleepy or stressed and be incapable to get points done during the daytime
• continuously worries about sleeping.
  

Causes of Insomnia: Insomnia is the most common type of sleep disorders.
As a result, they may get inadequate sleep or have inadequate sleep.
They would possibly not feel renewed once they wake up.
Insomnia can sap not only your energy level and mood but also your wellness, work functionality and high quality of life.
It can happen due to a disturbing occurrence like the death of a loved one, or loss of a job, or divorce.
It can also come in anticipating events to happen like weddings, vacations or holidays.
Sleep insomnia can also happen with jet lag, shifting work schedule, and other schedule changes.
Insomnia also can affect your daily activities and cause critical problems.
One example is, you might feel fatigued while driving.
Driver sleepiness (alcohol not related) is responsible for almost 20 percent of all serious car crash injuries.
Complications of insomnia: Complications of insomnia may include:

• your performance will be low on the job or at school
• your reaction time will be slowed while driving and higher risk of accidents
• Psychiatric problems, such as depression or an anxiety disorder
• Overweight or obesity
• Poor immune system function
• Increased risk and severity of long-term diseases, for example heart disease, high blood pressure and diabetes

Most adults have experienced insomnia or sleeplessness at one time or another in their lives.
An estimated 30%-50% of the general population is affected by insomnia, and 10% have chronic insomnia.
Research also shows that Women are the most frequent victims than men.
This disorder can happen at any age.
Nevertheless, older adults are usually more likely to have insomnia than younger people.