If doctor-prescribed, 1 mg Ativan (lorazepam) is safe to take for sleeping. It should be short-term though. Benzodiazepines can cause physical dependence, resulting in rebound-insomnia when you go off them.
You should discuss the use of Ativan with your physician. Because it is addictive, Ativan use should be monitored. There may also be a more suitable medication for your insomnia.