Benadryl may have addictive effects on some people who engage in long term use of the drug, especially for those taking the medication as a sleep aid. Taking more Benadryl to achieve expected results( dependence) is commonly seen.insomnia, low blood pressure and heart palpitations, tightness of the chest, an abnormal heartbeat or restlessness may be an indication to see a physician.this affects mental cognition, especially in the elderly. Confusion, periods of inability to focus or concentrate, and anxiety are some symptoms experienced, as are agitation, moodiness and impatience. Depression and fatigue may also be evident. Some individuals have complained of hallucinations, nightmares and coordination problems.Trembling, dizziness and vision complaints, including blurred or double vision are additional symptoms of the effects of long-term Benadryl use. Some people complain of a difficulty urinating as well as skin rash and headaches following long-term use. hoping that you are asymptomatic it is better to consult a qualified dr and get thorough body checkup to confirm the same and also line of management for regular sleep.