Wondering why you can't concentrate? Several physical and psychological factors can influence our ability to concentrate. If you want to improve concentration, you've got to address these factors head on.

  • Illness. Poor concentration may be the sign of an illness or disease. Studies show the onset of an infection and fever can zap your powers of concentration. Also, poor concentration is associated with several diseases and health conditions such as attention deficit hyperactivity disorder (ADD), depression, stroke, anxiety disorders, and Parkinson's disease. To improve concentration, schedule a visit to your doctor to have a physical examination and discuss your symptoms.

  • Stress. Sure, stress is a health condition, but it deserves to be mentioned separately simply because of the widespread impact it has. In a 2007 survey conducted by the American Psychological Association, nearly half of all respondents reported that stress had a negative impact on their personal and professional lives. Over a third were living with extreme stress, and nearly 50 percent believed their stress levels had increased in the previous five years.

    According to Mental Health America (MHA), chronic stress can cause poor concentration and memory problems. To reduce stress and improve concentration, MHA recommends contacting your doctor. Possible treatments will include better ways to manage the main stressors in your life, exercise, relaxation techniques, and taking medication or supplements.

  • Diet. Poor concentration and confusion have been linked to nutrient deficiencies, according to the Mental Health Foundation in the U.K. To improve concentration, try getting more vitamin B1,  which is found in whole grains, cereals and vegetables. Vitamin B12 is another nutrient that helps increase your focus; meat, fish, and dairy are good natural sources. The MHF also recommends getting more zinc found in foods such as tuna, salmon, cod, oysters, mussels, seeds and nuts.

    Also, some multivitamins are marketed to help improve concentration and energy. They often contain one or all of the following ingredients: higher doses of vitamin B12; ginseng; and gingko biloba. Before taking any multivitamin, get advice from your doctor to make sure you're taking one that's appropriate for your age, health status, and lifestyle

  • Insomnia. Poor concentration is one of the well-established complications of insomnia, along with daytime drowsiness and persistent fatigue. About 80 percent of insomnia cases are referred to as secondary (or co-morbid) insomnia, which means they're caused by another illness or health condition such as rheumatoid arthritis, diabetes, or chronic stress. Treating these health problems may remedy the insomnia and improve concentration, so schedule a visit to your doctor.

  • Medications and Other Drugs. Some drugs such as barbiturates and sleeping pills also cause poor concentration, reports the National Institute of Dug Abuse. Also, several studies have found that illicit drugs such as marijuana, cocaine and ecstasy leads to poor concentration, along with many other serious health problems. To help improve concentration, speak to your doctor about switching prescription medications. If you're abusing a drug the best way to increase your chances of recovery is to join a drug abuse treatment program.

  • Poor Time Management. Juggling several tasks, especially when you're pressed for time, makes it difficult to concentrate on any one task. Also, researchers point out that spending too much time on one task depletes both concentration and motivation - yet pushes stress higher.

    One tool that may improve concentration is a daily planner. Try to schedule tasks so that you complete them in chunks - one to two hours at a time each day. When completing a task, try to put other things out of your mind and remove any external distractions. Also, make sure you schedule in breaks for both reinvigoration and relaxation.

  • Age. Alas, getting older can limit your ability to concentrate. Research shows that gradual changes take place in the frontal lobes of the brain between ages 40 and 60 and cause poor concentration. To protect yourself from this brain change and improve concentration, researchers suggest that older adults reduce environmental distractions and focus on one key activity at a time.