Different people need varying amounts of sleep. If you only need 7 hours but are sleeping 9 hours, the 7 hour sleep spreads over 9 hours and becomes ineffective. You may try increasing daytime exposure to sunlight by getting out earlier. Often exercising can help or even spending time in meditation or prayer. Often medications that are prescribed for sleep can disrupt or eliminate the sleep cycle as described.
Antihistamines can also cause sleep depravation.
Some vitamins and minerals such as B6, niacin amide, calcium, magnesium, or antioxidants may help. Other herbal remedies to consider are Valerian root, Skullcap, Passion flower, Wood betony, or California poppy. Seema Agarwal is a licensed acupuncturist and volunteers her services at Women Alive.