For most people, things like hair color, eye color and straight (or crooked!) teeth run in the family. But for the Lopezes, a family who lives in Spain, it's something more serious: the sleep disorder narcolepsy.
The Guardian reported on the mysterious sleep disorder that affects many members of the Lopez extended family, a condition that causes people to doze off at a moment's notice.
The family is reportedly the first-ever example of an extended family having narcolepsy and cataplexy (a related disorder, where laughter or emotions cause sudden muscle collapse), The Guardian reported, and could shed some much-needed light into how the conditions form.
"The worst thing is boredom," David, one of the members of the Lopez family, told The Guardian. "If I am doing something I really like, or a project I am working at, then I can keep going for hours. The blood reaches your brain and keeps you going. But the moment you relax, the blood doesn't get there and off you go."
Narcolepsy is the term used for when the brain is unable to properly control cycles of sleep and wake, according to the National Institute of Neurological Disorders and Stroke. People with the condition will experience sudden bouts of sleepiness at any time, that can last from seconds to minutes. Cataplexy is known to be a symptom of narcolepsy, as are vivid dreams and hallucinations while sleeping, and times when the whole body seems to be paralyzed.
What causes narcolepsy is still not clear, though scientists believe it might have something to do with not producing enough of a protein called hypocretin, or possibly even something to do with the body's immune system, the A.D.A.M. Medical Encyclopedia reported.
Negative health effects of narcolepsy include having a higher risk of being overweight, but some of the biggest effects of the condition lie in how people perceive the people who have it, according to the Mayo Clinic. For example, people with narcolepsy may have a hard time with work or school because others just think they're lazy. Or they might have trouble with relationships because of the problems the sleepiness causes during sex, or the effects cataplexy has on emotions.
Right now, there is no cure for narcolepsy, though there are certain medications that can help a person to manage the condition, according to the Mayo Clinic. Lifestyle changes -- like planning naps so that you're less likely to have a sudden onset of sleep, and making sure to inform others of the condition -- can also be useful, the A.D.A.M. Medical Encyclopedia reported.