Rome, April 12 - As many as one third of prison inmates are at high risk of developing a mental illness, said psychiatrists gathered for a conference Friday. About 20,000 of the 70,000 inmates in Italian prisons have developed diseases such as psychosis, depression, severe anxiety, and bipolar disorder, say the experts gathered for a national congress of young psychiatrists. Some were mentally unwell before prison; others developed disorders once inside what some have described as "hell," according to the psychiatrists. Early investments in mental health - before people become so ill that they commit crimes and wind up in jail - would be money well spent, the experts say. The statistics show "everything that happens after years of neglect on the part of Italian mental health services, and this is the bill that must be paid," said Claudio Mencacci, president of the Italian Society of Psychiatry. In fact, prison inmates are nine times more likely to attempt suicide than in the general Italian population - and that rate is quickly climbing. Since 1960, a 300% increase in prison suicides has been reported. Guards dealing with prisoners are also becoming less mentally healthy, the experts say: between 2000 and 2011, 68 suicides were reported among Italian prison workers. Overcrowding in prisons contributes to the problem. Italian prisons are among the most crowded in Europe, with as many as 150 inmates per 100 beds, compared with an average of 107 in the rest of Europe.