Through a complex series of signals to the brain, acupuncture increases the amount of certain substances such as serotonin, which promote relaxation and sleep. A study in 2004 found that in patients with anxiety, acupuncture increased nighttime melatonin production and total sleep time. The patients who received acupuncture also fell asleep faster, were less aroused at night, and were less stressed.
Another study found that acupuncture improves sleep quality in patients with HIV, among whom sleep disturbance is a common problem. The researchers found that, “Sleep activity and sleep quality significantly improved following 5 weeks of individualized acupuncture…”
Other studies have shown that acupuncture works for people without health problems, too. A study in 1999 found that acupuncture improved sleep quality in normal people with insomnia.
Acupuncture can also help with insomnia that occurs during the onset of perimenopause.
If you’re into research, here’s a systematic review of acupuncture and insomnia: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3156618/
(although reading studies may cure your insomnia alone!)