The 11 -- YEAR-OLD had slashed his wrists.

"I want to go to heaven," he sobbed. "I can't stand these stomachaches and being unhappy . . . If I could only die . . . It's hard to live . . . Living is horrible. I just want to die because nobody cares if I die, so I just want to die."

Childhood, we are told, is supposed to be a time of joy and carefree innocence, but for this boy and many others it is so sad and painful they want to die. The poet's halcyon days of youth -- easy, happy, golden --somehow elude them, and they want out of life even before they are old enough to understand the permanence of death.

For years the experts questioned whether young children could really suffer severe depression and intentionally seek death. Now it seems clear that they do both, and that many "accidents" -- like swallowing poison or darting into heavy traffic -- are in fact conscious or unconscious suicide attempts.

Consider, for example, these attempted suicides:

A 12-year old girl hung her doll by its neck, drugged her little sister, cut both of her own legs with scissors, slashed her wrists and overdosed on hypnotic drugs. "I would be better off dead," she explained. "Then no one will ever have to look at my ugly face again."

An 11-year old boy tried to kill his dog, attempted to suffocate his baby brother with a pillow, and stabbed pins and needles into his own stomach. Asked why, he answered, "Because Mother doesn't have any love in her heart for me."

An 11-year old boy, preoccupied with death and the idea of rejoining his dead grandmother, threatened to throw himself in front of a car, beat and disfigured his own face, and finally jumped out the window of a two-story building.

A 5-year old girl burned her 3-year-old sister and tried to choke her with a shoestring, threatened her mother with a knife and fled from the house into heavy traffic.

A 6-year old boy who wanted to die "because nobody loves me" first cut himself with his father's razor and was later found hanging from a second-story window. The Trauma of Family Conflict

THE WISH TO DIE can be based on misconception -- in some cases, it can be a wanting to be dead just for the moment, since most children don't comprehend the finality of death before about the age of 8.

But the medical psychologist who studied these suicidal children at the Neuro-psychiatric Institute of the University of California at Los Angeles says his findings "demonstrate that pre-teen-age children can experience the pain of life to the point of wanting to die." Said the psychologist, Morris J. Paulson: "Aloneness, fear of rejection and threats of violence are as meaningful to a 4-year-old as to an adult."

Of the nearly 2,000 children and teen-agers in the United States who killed themselves in 1976 (the latest year for which figures are available), fewer than 200 were under 14. But many suicides go unreported, and Paulson says so-called accidental injuries and poisonings in school-age children are often "purposeful selfdestructive acts."

For example: One-fourth of the admissions to the psychiatric unit at Children's Hospital of Los Angeles-Edgemont Hospital during its first year of operation have involved suicide attempts or a preoccupation with self-destruction, according to Dr. Howard Hansen, head of the division of psychiatry there.

The suicidal children at UCLA were mostly boys. Nearly half were failing in school despite normal IQs. Many had no friends. Some complained of physical ailments, while others turned their inner hate and anger on others.

The economic level of the family -- most were low-income, semi-skilled and with high school educations -- did not seem to matter. Paulson and his colleague Dorothy Stone had found similarly suicidal children in an earlier study of more affluent families.

What did matter was the emotional poverty found in nearly all the families of suicidal children (some of whom had close relatives who had also attempted suicide): more than half the parents were separated or divorced; the remainder could hardly be said to be living in harmony.

As Paulson describes it: "For the younger aged children, the most frequent immediate event leading to referral [to the clinic for treatment] was perceived or imagined abandonment by a parent figure.For some families, divorce was the ultimate separation of a hostile, feuding, pathological relationship of violence between husband and wife."

In other families, Paulson said, the birth of a new brother or sister -- a rival for the parent's love -- and the mother's decision to go back to work were interpreted by the child as rejection.

"For many older children," Paulson continued, "the witnessing of family violence, both verbal and physical, precipitated acute panic, fear and concern that they also may be the next victim of violent assault."

Said an 8-year-old girl: "They don't like me. I wish I was dead."

And another: "I would rather die than be spanked. They want me dead."

A battered 10-year-old whose 13-year-old brother had committed suicide earlier was philosophical: "Everyone kills and everyone dies. . . There is no escape." Depression in Children?

DEPRESSION is the leading cause of suicide. The psychiatrist who heads the only U.S. hospital ward devoted to studying childhood depression, Dr. Joaquim Puig-Antich of Columbia University, estimates that at least 1 percent of all children are depressed. This is based, in turn, on estimates that 10 to 15 percent of children in urban areas have some psychiatric disorder and that in 5 to 10 percent of the cases the disorder is depression.

When psychiatrists talk about depression, however, they are talking about much more than just feeling blue. And sometimes much less than wanting to die.

No one denies that children feel sad or discouraged at times, says UCLA psychiatrist Dr. Gabrielle Carlson. Or that they may feel depressed at being separated from a loved one or at being trapped in a miserable environment. The controversy among professionals has centered on whether children can suffer adult-like psychiatric depression: an illness with definite signs and symptoms, a family history of related disorders, certain biochemical levels in the body and a predictable response to anti-depressant drugs.

Studies by Carlson, Puig-Antich and others show that they do; whether they will outgrow it or become depressed adults is another question that will require long-term follow-up studies because depression most often first shows up when a person is in his 30s.

What, then, does a depressed child look like? Carlson says, for starters, that most will readily admit that they feel sad or down if anyone bothers to ask. They may, however, also have a behavior disorder like hyperactivity that draws more attention: "When a kid comes in who's been burning down the house, you don't stop to do a depression inventory," Carlson notes.

The depressed child may also be irritable and weepy. Other symptoms include: thoughts of death or suicide, tiredness, withdrawal from other people or aggressiveness and getting into fights, loss of interest in things that used to be fun, guilt feelings, poor concentration (and consequently, poor performance in school), insomnia or sleeping a lot, and, sometimes, changes in appetite and weight. If a child appears sad and has as many as five of these symptoms for more than a couple of weeks, chances are he is depressed. Heredity Plus Trauma

THE CURRENT VIEW of how depression develops in children goes like this.

Depression runs in families. But children born with a susceptibility to the disorder -- a "high genetic load," in scientific parlance -- may not become depressed until later in life, if ever, unless they are also subjected to traumatic events -- separations, divorce, cruelty, neglect, the death of someone close -- during their first five years.

"The child has to be hit both ways," Puig-Antich explained.

Blood samples from severely depressed children have shown an excessive amount of cortisol, an essential hormone secreted by the adrenal gland whenever the pituitary gland releases a certain hormone. Measuring such hormone levels gives reasearchers a sort of window on the brain: The brain chemicals that have been implicated in adult depression -- serotonin norepinephrine and dopamine --tem, thought to be the seat of the emotions. The limbic system, in turn, regulates the pituitary. So the amounts of hormones in the blood and breakdown products of these brain chemicals in the urine provide clues as to what's going on up in the brain.

The drug that seems to wipe out depression in these children is imipramine (Tofranil). Imipramine is not used for more than three or four months, Puig-Antich said, and only to alleviate the depression so that other therapy can be started. "It's a losing ball game to try to treat with psychotherapy while they are still depressed," he explained.

Since interest in childhood depression only began in the 1970s, much remains to be learned about the illness and how to prevent or treat it.

But simply being on the lookout for what the experts now seem to agree is a not-so-rare illness is an important first step. Paying attention to "accidents" and indirect symptoms and school problems and loneliness and temper tantrums, UCLA's Paulson says, puts us "in a better position to intervene in the identification, early treatment and ultimate recovery of severely depressed children who say. 'I'm bad, and I want to die."