Caffeine is addictive. Even if you drink only one large cup of coffee (or three cans of a cola drink) per day, you may feel the ill effects of missing a 'dose'. The symptoms of caffeine withdrawal include headaches, drowsiness and loss of concentration. Drinking coffee will relieve these symptoms, so it can become compulsive. Caffeine in high doses can make anyone anxious but, in vulnerable people, even one cup of filter coffee can result in symptoms similar to a panic attack.