While nightmares are more common among children, 50 percent of adults have nightmares. These frightening, often realistic dreams can leave us feeling rattled, and in more severe cases they can cause sleep deprivation which is linked to heart disease, obesity, and depression. There are a number of things that can cause nightmares, including:
Eating before Bed: A pre-bedtime snack can increase your metabolism, which causes the brain to become more active and can sometimes lead to nightmares. If you notice that you have more bad dreams after having a late-night bite, make a goal not to snack after dinner, or at least to avoid heavy meals right before bed.
Medications: Prescriptions that affect chemicals in the brain (such as antidepressants), as well as some blood pressure medications, have been linked to nightmares. Talk to your doctor to see if a different drug or a lifestyle change might be a better alternative.
Lack of Sleep: It's a vicious cycle: not enough sleep may lead to nightmares, and having nightmares can cause a lack of sleep. If you notice that your nightmares increase when you've been skimping on sleep, be sure to practice a proper sleep routine (like winding down before bed with a relaxing activity and keeping your bedroom cool) to increase the time that you spend sleeping.
Sleep Disorders: Sleep problems such as sleep apnea and restless leg syndrome may cause nightmares. Ask your doctor about treatment options if you suffer from a sleep disorder, since treatment may help improve the quality of your sleep and help prevent the nightmares.
Stress: Anxiety and post-traumatic stress disorder can both lead to nightmares. If you're extremely stressed, talk to your doctor about coping mechanisms, including lifestyle changes, psychological counselling, and/or medications.
Source: Sleep.org