The New York State Psychiatric Institute in Manhattan is performing its little-known but extensive Prozac experimentation on troubled kids as young as 6 years old, according to internal records.

Prozac has been approved by the federal Food and Drug Administration for adults only and is not recommended for children under 12.

Several experts say the popular antidepressant is virtually useless in treating most kids with mental problems, and they warn that it could harm them.

But information about Prozac's most serious side effects was often not shared with the kids recruited as research subjects, or with their parents.

The Prozac experiments are detailed in nearly 2,500 pages of documents obtained by The Post from the state Office of Mental Health under the state's Freedom of Information Law.

Those documents provide a chilling look at scores of state-authorized experiments under way in the city that offer little or no direct benefit to their human subjects - who are often children or adults suffering from serious mental disorders.

The OMH documents describe experiments in which:

*Painful and debilitating spinal taps are being performed on severely depressed youngsters.

*Kids suffering from anxiety disorders and depression are being put in stressful situations.

*A potentially harmful - and sometimes fatal - drug that causes painful side effects is being given to kids and adults with volatile behavior problems.

The documents also show that a risk to patients well known to psychiatric researchers - that some Prozac users experience heightened suicidal thoughts and violent behavior - was withheld from the kids recruited and their parents.

While the potential deadly danger was cited in the researchers' documents, it was not included in the consent forms given to children and their parents to read and sign.

"Some patients have been reported to have an increase in suicidal thoughts and/or violent behavior," note researchers' documents describing the risks involved in an experiment to test Prozac on 30 severely depressed patients ages 12 to 18.

But this is not mentioned in the four-page consent form.

Federal rules require that research subjects, including children and their parents, be told of potential risks before taking part in experiments.

"This is a smoking gun," said Vera Hassner Sharav, president of Citizens for Responsible Care and Research in Manhattan.

"Subjects are supposed to be informed fully of all the risks and side effects, [it should be] written on the consent form. That is absolute."

Another major potential Prozac side effect - wild manic episodes - also was acknowledged in researchers' internal records but was not included in some of the consent forms examined by The Post.

The consent forms, approved for use by the New York Psychiatric Institute last year, refer only to the possible lesser side effects of Prozac, such as nausea, headache, weight loss, fatigue, nervousness and sexual problems.

"Doctors and researchers don't tell the subjects the dangers," said Dr. Peter Breggin, director of the Center for the Study of Psychiatry and Psychology and a critic of giving Prozac to children.

"It has a tendency to make [kids] psychotic," said Breggin, author of "Talking Back to Prozac." "It's a very dangerous drug to be experimenting with children."

While instances are rare, some doctors have reported that patients on Prozac experienced suicidal tendencies, violent rages, insanity, hallucinations and mania.

Critics charge some researchers intentionally hide the most serious side effects because they fear full disclosure will frighten people away from the experiments or will taint the results by planting ideas in patients' heads.

Although Prozac - which affects the brain chemical serotonin that is linked to mood and emotions - has been approved by the federal government for use only by adults, doctors are not precluded from prescribing it for kids.

They have been doing so with increasing frequency across the country, even though consumer drug guides state that Prozac is not recommended for use by children under the age of 12.

Records show that at least four experiments using Prozac on young children have been undertaken recently by the New York State Psychiatric Institute, including one funded by Prozac's manufacturer, Eli Lilly Co.

That study, to determine if the drug is effective on obsessive-compulsive disorder, uses 22 subjects who are 6 to 18 years old.

Another study approved by the state is for 20 children as young as 8 years old.

State Office of Mental Health spokesman Roger Klingman said no children in any of the Prozac studies have experienced any adverse effects.

OMH refused to release experiment "incident reports" that describe things that may have gone wrong.

Klingman noted that only one child to date had been enrolled in the study that cites suicide and violence as possible side effects, and said the child and family were counseled about suicide.

He said the experiment's procedures are currently being revised before further subjects are enrolled.

Klingman said information linking Prozac to heightened suicidal thoughts and violent behavior wasn't included on the consent forms, despite being noted by researchers, because the FDA has found no connection between the two.

And no disclosure linking Prozac to wild manic episodes was made to patients, he said, because the side effect has been cited only in manic depressives, and those weren't the type of subjects sought in the experiments.

Dr. Donald Rosenblitt, an expert on Prozac, warned that the antidepressant drug can trigger psychotic episodes in seriously disturbed youngsters, and that the drug's long-term impact on kids remains unknown.

"We simply do not know what the effect of drugs on children before the age of 7 is," said Rosenblitt, clinical director of the Lucy Daniels Center for Early Childhood in Cary, N.C.

"The brain is still ... developing up to age 7. The jury's absolutely still out."

The experiments and consent forms were given the green light by the psychiatric institute's internal review board, which is supposed to ensure that studies are ethical and all state and federal rules are followed.

The institute is under federal investigation in a probe believed to be focused on the use of kids in since-discontinued experiments with fenfluramine - a drug linked to heart problems.

Some psychiatrists believe Prozac research involving young subjects is needed because the drug is being widely administered to children by doctors.

"I'm glad to hear research is being done," said Dr. Peter Kramer, a psychiatrist and author of the best-selling book, "Listening to Prozac."