THE AMERICAN Psychological Association estimates there are 100,000 people in the Washington area receiving some kind of professional help for mental anguish. I know of a way to cut that figure in half without lying down on a couch or swallowing a pill.

Go fishing.

I've always felt that fishing is the best therapy, the best social leveler and the best hook for crocheting relationships together, whether it be boy-girl, wife-husband, father-child or just a couple of acquaintances -- even if they happen to be world leaders.

I always felt safer when Presidents Harry Truman, Dwight D. Eisenhower and Jimmy Carter took off their choking ties and starched shirts and went fishing. I knew they would come back to their desks more sane, more energetic and more humble.

If I ever became a presidential handler -- a dim prospect, happily for the country -- I'd arrange for Ronald Reagan and Soviet leader Mikhail Gorbachev to go off fishing together on a river or stream where they'd be sure to get strikes from acrobatic fish, like trout. I'd equip them with spinning rigs and spoons, because they're easy to cast and reel in. And I'd make sure they were left alone.

I know from 35 years of taking people fishing just what would happen. There would be a mutual stiffness at first; followed by embarrassment over not being able to cast well; followed by warm laughter at each other's efforts; followed by the spine- tingling excitement of a sudden strike; followed by the loss of the first fish as they let the line go slack and the hook be thrown while watching the leaps and runs of the fish in awed admiration. Finally, there would be conquests of the fish, bonding them in a feeling of mutual accomplishment and warm weariness.

After they had caught a dozen fish between them, I'd order the American and Russian horseholders to come out of the woods, to start the wood fire, to fillet and broil the fish and to open the chilled wine. Only then, over wine and fresh broiled trout, would I allow fellow fishermen Reagan and Gorbachev to talk about the world's problems. Get rid of those paper agendas with Roman numerals I, II, III and sub paragraphs A, B and C written by bureaucrats who've never caught a fish.

Climbing down from this proposed Fishing Summit, let me prescribe some ways we ordinary folks can get the most therapy out of fishing.

The key is to make the contest between you and the fish a fair fight, one against one, if possible. Casting a fly upstream to entice a fussy trout is more than a fair fight, one I seldom win. Standing on the bank of a river, stream or pond plugging for bass is also close to an even match. Standing or sitting on a bridge or fishing pier is delightfully diverting if you enjoy the human comedy and don't mind starring in it on occasion when your line gets tangled with the next guy's.

And hurling a lure or bait out over the first big waves of the ocean in hopes of drawing a fish to your offering rather than the smorgasbord of natural goodies all around him is the height of optimism, some would say idiocy.

But surf casting is my favorite type of fishing, rain or shine, wind or calm, heat or cold. And I've tried almost all kinds of fishing. The addicted surf caster will not tell you this, but he doesn't really care if he catches a fish. The therapy and joy come from watching the ocean and the birds, hearing the hiss of the foam as the waves retreat from around your feet, and completing a long cast. Surf casting at dawn is pure poetry on a morning when the sun explodes on the horizon. Actually catching a fish is one of those rare events that stays fresh in your mind for years afterward.

For my money, the least therapeutic type of fishing is that offered by skippers who roar out on bay or ocean in noisy, diesel-powered boats, jam broomstick fishing poles with reels of thick line into fish holders, and tell their paying customers what to do and what not to do any time a fish is hooked. Trolling is an unfair fight for the fish, which is virtually drowned by the forward motion of the boat no matter what the fisherman does. Chumming for bluefish -- anchoring and baiting the water around the boat with ground-up fish -- might sound less therapeutic than trolling. But chumming can be more so because it's you against the fish. The boat doesn't drown it.

The Washington area is blessed not only with Chesapeake and Delaware bays, lakes, ponds and streams but also with the Potomac River. The Potomac, for all its troubles, is a glorious resource. Those who have discovered her therapeutic wonders include the men, women and chilren I see lined up before 7 a.m. these spring mornings at Fletcher's Boat House, waiting for it to open so they can get out on the water in a rowboat for some one-on-one with the fish lurking in the holes. They'll come off the river more at peace with themselves and the world, no matter if they catch anything. What shrink can promise that?