Drug dosage can be adjusted, or the time of day a drug is taken can be changed. Nutritional and vitamin status should be tested and deficiencies corrected. Quality sleep will often return. They are nicotine and caffeine. Caffeine can interfere with sleep up to twenty hours after you consume it.
Caffeine is also present in colas, chocolate bars, and cocoa.
Even headache remedies and diet pills contain caffeine. And the truly interesting aspect of caffeine is that it can cause both insomnia and sleepiness. I've seen countless patients who had trouble getting out of bed in the morning, until they eliminated their caffeine. In response to caffeine, the body's nerve cells fire more rapidly, giving a feeling of alertness and energy. Unfortunately, a crash must follow the high, and caffeine users interpret that crash as a sign that more caffeine is needed.