IF this Hallowe'en is like most others, there'll be a rush on the video shops for horror movies. Children and teenagers like horror. They like Point Horror books and the Goosebumps series, they like horror movies, like Nightmare on Elm Street (parts 1 to 1,000) and The Stepfather and The Candyman.

It's parents who are afraid.

We understand our children's grisly fascinations up to a point, but then we get panicked about video nasties, grumble about the books and try to get the whole thing under control.

There's every reason, of course, to be concerned. But no matter what we say and do, many children and . . teenagers vote with their feet: they want to be scared.

Their first taste of horror probably comes from fairy tales, which even in sanitised modern versions are tales from the darkside. In Snow White, a wicked queen, jealous of her stepdaughter, orders a huntsman to slay her and cut out her heart. Hansel and Gretel are thrown out of their home by another stepmother and nearly baked alive by a witch.

Nowadays, children progress from this rapidly, through Hocus Pocus, Gremlins and the like on video, onto the Goosebumps series of books - "spooky, funny, scary", according to Waterstone's children's book buyer Sarah Webb.

By the time they're 12, 13, and 14, do they want to watch the videos from the horror section of your neighbourhood shop? You bet they do.

Michelle McCoy, owner of The Video Shop in Sandycove, Co Dublin, says: "You have to be really careful, kids aged 12 to 15 are always trying to get out stuff rated for 15 or 18 year olds".

Horror sections of video stores include everything from The Fly (gross) to The Stepfather series (serial stepdad kills all his families) to The Hellraiser series (returns from dead to kill) to Stephen King chillers, as well as recent remakes of Dracula and Frankenstein. Ironically, many are the kind of movie that only somebody aged under 18 would watch: you'd worry about anyone older who liked most of these movies.

But why do children and teenagers like horror so much?

Andrew Conway, senior clinical psychologist at the Mater Child Guidance Clinic, in Dublin, says: "The bottom line is, people like to be thrilled. It's why people go on the rides at Disneyland or Alton Towers. It's the thrill, the buzz, the adrenalin racing, it's organised terror. Some kids are natural dare devils, some won't go on the rides at all, and some will go to say they've done it. Horror movies are much the same.

The fascination with bodily functions, a feature of many of the films, is many teenage boys' way of coming to terms with their changing bodies.

The problem, he says, is that some horror movies can have a terrible downside. Some will seriously upset a sensitive child; others may lead what he calls a "poorly censored" child to copy something thrilling he or she sees in a movie. This is the child or teen who, for whatever reason, has no internal censor, who can't tell fantasy from reality. "The teenager who, especially if there's drink involved, might kick a cat to death, or throw it on a bonfire."

Marie Murray whose recent study of teenagers' television and video viewing habits showed that 45 per cent of parents of first year secondlevel students i.e. children aged 12 and 13 allowed them to watch 18 certificate movies.

Like Murray, Conway is shocked. He says categorically that parents should be guided by the certificates that label a film suitable only for children of a certain age and over, and simply not allow underage children to watch them.

The good news for parents is that the genre seems to have run out of steam, at least for the moment. The most successful (films like the Halloween and Nightmare on Elm Street series) have been drained of their last drop of blood, and any teen, looking for a new horror movie this week will have to look hard.

The X Files (out on video as well as on TV) has taken a lot of the teen audience, and interestingly, has a lot of adult approval.

Irish Times film reviewer Hugh Linehan reckons that many horror themes have passed into mainstream movies. He points to Seven, a kind of chiller thriller starring Brad Pitt and a pretty nasty ending which, according to Linehan, lacks the jokey quality of a lot of the really OTT shlock horror - the jokey quality, for example, of a now cult horror movie like Sam Raimi's Evil Dead, which caused a furore over a decade ago. (Not surprisingly: it features a woman raped by a tree).

BUT people like Linehan, in his early thirties, and Sarah Webb, 26, grew up watching movies like this, and grew out of them. (Webb says she liked blood seeping out of the walls in films like the Amityville series.) And mainstream movies like Trainspotting, hugely popular with teenagers, have the same intimate depiction of bodily functions which is another feature of the horror genre. Teenage boys, in particular, seem to find anything that adults would find gross and disgusting particularly satisfying.

When our children are small, it is easier to judge how much "terror" they can take. Some laugh at a movie like Gremlins (small, furry, evil creatures). Others won't sleep for a year. But as they get older, we should keep informed about what they're reading and watching.

Webb recommends that parents read Goosebumps and Point Horror books. And Marie Murray has said that clinical research findings show that it is the absence of an adult voice or interpreter that renders television and videos more confusing and harmful.

I think what all this means is that if you're going to let your child watch a horror movie, especially an underage child (and yes, I have), you'll have to watch it yourself first, a real challenge if these movies really scare you.

It means being a parent who does the responsible thing and checks with other parents before letting your child's friends watch a scary video. And this may well mean conflict.

It means (okay, I've said it before) feel the fear and really find out what horror books and films are all about anyway. You have been warned...