“Without a doubt, sleep is the biggest issue for homeless people,” writes San Diego-based blogger and self-proclaimed “chronic homeless man” Kevin Barbieux, who writes under the name The Homeless Guy. Barbieux, who has alternated between transitional housing and no housing at all, updates his blog either through his donated laptop or by using the computers at his local library.

“Homeless advocates are always focused on what are believed to be the root causes of homelessness, and providing the basics of food shelter and clothing to those who do without,” he continues. “And although those things are important in their own way, they don't affect homeless people with the intensity that sleep does (or the lack thereof).”

For individuals without permanent housing, sleep is difficult to come by. When there’s no way to secure your personal belongings, it’s dangerous and frightening to be as vulnerable as we are when we’re in a truly restful sleep.

As a result, sleep becomes a matter of when-you-can, where-you-can. And often, you just can’t, leading to a host of other mental and physical ailments.

Sleep deprivation has also been linked to an increase in mental illness, drug abuse among teenagers, and higher rates of violence and aggression. Schizophrenia-like symptoms may also start to develop, which is problematic in a population that already experiences a higher-than-average likelihood of suffering from the disease.

The dangers of the elements (in colder climates, even nodding off in the winter may be a death sentence), the possibility of attack, and the physical maladies that arise from perpetual dampness and grime make achieving good sleep an impossible feat.

Even finding enough ground to stake out can be difficult. The discomfort of homelessness has driven businesses to extreme measures. In London, some buildings have erected “anti-homeless spikes.”

There are also potential legal ramifications. The National Law Center on Homelessness and Poverty has found that “of 234 American cities, 40 percent make it a crime to sleep in public spaces.”

Barbiuex notes that shelters, which are often considered to be the safest, best option by those who aren’t homeless, come with their own set of problems. As he writes in his blog:

You check in to a homeless shelter and hope for the best. But the ‘best’ is not offered at shelters ... After a long period of processing and standing in lines... you'll finally be assigned a bed. You'll find this bed is located in a large warehouse type room with many other beds—more than likely they will be bunk beds, or army cots, (ever try to sleep on an army cot?) You will be in a room with anywhere from 25 to 150 other homeless people, and not all of them will be ready to go to sleep. They will be talking, laughing or yelling, getting into fights (verbal and physical) making noises, the mentally ill will be trying to wind down from their constant hallucinations. As is practiced in many shelters, you'll be required to undress, give your clothes over to shelter personnel to be placed in a closet, you'll have to wear hospital scrubs. You'll be given one thin blanket, regardless of the temperature, you may, or may not be issued a pillow. If you like the cold, you'll sleep well, if not, you could have problems ... After a couple hours, most everyone has settled in to sleep, and you'll get some sleep. But then you'll be awakened, sometimes rudely, at 5 a.m. at most shelters. 5 a.m. every single morning.

Most shelters make it a practice to eject guests long before white-collar workers rise in the morning. By 6 a.m., homeless men and women are wandering the streets, trying to find an open Starbucks or a bus to hop on to catch an extra few moments of shut-eye. By the 8 a.m. commute, they are hidden in plain sight, either in day shelters, or in the doorways and alleys where you’ve probably seen them nodding off.