Well we do have cases where people have been stranded for example and starved that way. It most certainly does cause a great deal of mental disturbance. Think of the Chilean plane disaster for example. Most people turn to cannibalism when they have no other option and there are dead people around. But also many other single cases of people being stranded. People who self starve e.g hunger strikes also report great mental disturbances, hallucinations, confusion. There are cases of prison hunger strikes ... this looks promising...
What Happens on a Hunger Strike | Fasting
excerpt
"After the third day of a hunger strike, the body starts to use muscle protein to make glucose, a sugar that's needed for cell metabolism. Levels of important electrolytes, such as potassium, fall to dangerous levels. The body also loses fat and muscle mass.
After two weeks, people on a hunger strike may have difficulty standing; they can also suffer from severe dizziness, sluggishness, weakness, loss of coordination, low heart rate and a chilled feeling.
Low levels of thiamine (vitamin B1) become a real risk after two or three weeks and can result in severe neurological problems, including cognitive impairment, vision loss and lack of motor skills.
Permanent complications and death
After more than a month of fasting, or when more than 18 percent of body weight is lost, severe and permanent medical complications can occur. It can become very difficult to swallow water, hearing and vision loss can occur, breathing can become labored and organ failure can start to set in.
Beyond 45 days, death is a very real risk, due to cardiovascular collapse or severe infection.
Aside from the physical damage suffered by hunger strikers, psychological changes causing impulsive and aggressive behavior are common. These effects can "enhance the likelihood that [hunger strikers] will starve themselves to death," according to a report from the Journal of Medical Ethics.
Even after a hunger strike ends, refeeding has some real risks, since the metabolic changes that occur during severe fasting can be profound."