If you've ever been jolted awake by your alarm clock but were so momentarily confused that you reached for the telephone instead of hitting the snooze, you likely experienced an episode of what's called "sleep drunkenness." And you're not alone.
In a new study, researchers found that sleep drunkenness may affect one in every seven people. The disorder causes a person to be so confused upon being woken up that they don't know what they are doing.
The study, published Monday in the journal Neurology, also determined that 84 percent of people who experienced an episode of sleep drunkenness also suffered from a related sleep disorder, a mental health disorder or were taking psychotropic drugs such as antidepressants.
Episodes of sleep drunkenness tend to occur during or following forced arousals from sleep, typically either during the first part of the night or in the morning. Similar to sleepwalkers, people who suffer from sleep drunkenness are not aware of their actions, which can sometimes even be violent, potentially causing harm to themselves or others. People may also not remember what they did during an episode of sleep drunkenness.
"These episodes of waking up confused have received considerably less attention than sleepwalking even though the consequences can be just as serious," study author Dr. Maurice M. Ohayon, of Stanford University School of Medicine in Palo Alto, California, said in a statement.
For the study, researchers interviewed 19,136 people age 18 and older about their sleep habits, and asked them whether they had experienced any symptoms of sleep drunkenness. The people in the study were also asked about mental illness diagnoses and any medications they took. Fifteen percent said they had experienced an episode of sleep drunkenness in the past year.
The investigators found that there are certain factors that seem to go hand in hand with the condition. For instance, they determined that almost 71 percent of the people with sleep drunkenness also suffered from another sleep disorder, such as sleep apnea.
And, among the people who had experienced an episode of sleep drunkenness, 37.4 percent also had a mental health disorder. Study participants who suffered from depression, bipolar disorder, alcoholism, panic or post-traumatic stress disorder and anxiety were at a higher risk of experiencing sleep drunkenness. About 31 percent of people with sleep drunkenness were on psychotropic medications such as antidepressants.
Getting more -- or less -- than the typical 7 to 8 hours of sleep a night was also linked to the incidence of sleep drunkenness. About 20 percent of people who typically got less than six hours of sleep per night, and 15 percent of those who got more than nine hours, experienced the disorder.
The researchers noted that less than 1 percent of the participants with sleep drunkenness had no known cause of the disorder or did not suffer from a related condition.
"These episodes of confused awakening have not gotten much attention, but given that they occur at a high rate in the general population, more research should be done on when they occur and whether they can be treated," Ohayon said. "People with sleep disorders or mental health issues should also be aware that they may be at greater risk of these episodes."
Interestingly, the researchers speculated that root of the disorder might have something to with adaptation and ability to react to a potential threat. They noted that when animals are awoken suddenly from their sleep, the inhibition of their startle reflex is reduced.
"This mechanism has a protective role for the survival of the animal, which needs to respond quickly to potential threats when it is suddenly aroused," they wrote in the study. "A similar protective mechanism probably exists in humans," and therefore techniques that are used to suddenly awake a person in the morning, such as using the alarm clock, can trigger this defense mechanism and provoke episodes of the disorder.