Hi Julia. When there’s no obvious cause for persistent insomnia then I think it’s down to low GABA, like daz84596 mentions. My own view is also this is the reason people fall asleep more easily if they consume alcohol or sleeping pills because they both increase GABA. Chronic long term stress and anxiety lower GABA.
Yep, but remember that alcohol and sleeping pills are not long term solutions for sleeping problems; in fact some might question the efficacy of using them even short term. Do note that an out-of-sync circadian rhythm can also cause sleeping issues; light therapy in the day can be used to reset this, or simply get more sun if you are in a country which has it year round 
Absolutely. Alcohol and sleeping pills are not a long term solution. Relaxation techniques help increase GABA but not everyone responds to it. Individual cases need to be investigated by sleep specialists if the insomnia is severe and persistent to see what treatments are available - possibly drugs that are used “off label” for insomnia.
How are you now?