Grace Dent: So cannabis affects your IQ. Or is it the hours spent eating Peperami and watching Cheech and Chong?

It's official: heavy cannabis use as a teenager makes us stupider adults, knocking an average of eight points off your IQ. For today's grown-ups, those are the missing points fooling you into remembering Cypress Hill's whiny stoner dirge as "really excellent music" (it doesn't, it sounds like a man with a sinusitis reading sections of the phonebook) or believe Up In Smoke by Cheech and Chong (two twonks in a van repeating themselves endlessly) as a comedy classic.

If you spent the Nineties doctoring WD-40 cans, your parent's best cutlery set, fish tanks, demi-johns and buckets in a bid to ensure your personal weed level never fell below "really bloody mangled", there's a chance your A-level revision for French verb endings fell somewhere short of "slapdash".

We're talking heavy cannabis usage here. Not the majority of British 30somethings who had a few honks on a clumsy three-skinner around the back of a school disco, felt a bit wonky and spent a surreal journey home in their mother's Volvo estate listening to their mother's Daniel O' Donnell CD through a freshly blown mind. You guys are OK. Don't hand yourself in at A&E just yet. Tiny amounts of cannabis don't really do anyone a lot of harm. They just might make you walk a long way at 3am to buy Mr Kipling's individual apple pies or consume something unwise like a Peperami.

Continual large amounts of cannabis, however, makes people quite boring, curiously tired, underachieving and cosy in the eco-climate of their less than lemon-fresh underwear. It's one of the worst drugs. At least MDMA tempts one to leave the house and enter clubs or dark raves, chat to strangers and imagine oneself, temporarily, as a heavenly creature lighting up dance floors.

At least acid tends eventually to give people a big scare that stops them ever repeating the drug. Heavy cannabis users just trudge on and on –often from teen years to adult life – in one long spliffy groundhog day. Men: try adding "I smoke a lot of weed" to your internet dating profile and enjoy your long stoned walk in the sexual Gobi desert. Sane women have no interest in long-term heavy cannabis users as weeping "But, Zane, you said we'd go to Ikea the last five weekends!" at a lump in a tracksuit with unclipped werewolf-style toenails is terminally wearing.

"Freeing the weed" is not one of my political views. Weed made me listen to Morcheeba. I can't forgive it for that. Obviously, trendy liberal types like me (apparently this is what I am, according to my mailbag) aren't supposed to say this as this would be "getting tough on drugs", which I have no plans to do. Massive weed smokers don't need our anger or penal strength, they need our gentle and merciless derision. I suggest you start by typing the words "Puff Puff Give" by HannaH's Field into YouTube and savour the toke-tastic twaddle of a pro-weed smoker bashing away on bongos, proclaiming that weed "comes from the earth, the earth can't hurt" (HannaH was stoned the day her school was teaching her about Deadly Nightcap mushrooms and the contaminated earth around Sellafield).

Dear God, I saw the greatest minds of my generation fail their A-levels and still get thirds in sociology, and then sit in a ropey tattoo parlour having a green cannabis leaf inked onto a forearm with the legend "LEGALISE CANNABIS" beneath. "What do you think?" my ex-boyfriend asked, slumped on the shop's back step, haphazardly erecting a single skinner of Red Leb lest he gain a clear mind for one minute and realise he'd neither sent off his Ucas form nor changed his Kappa hoodie top, a Jackson Pollock of curry-sauce flecks, hot-rock holes and WD-40 stains, in weeks. "It looks like a shit shamrock," I said. I split up with him soon after and it took him eight weeks to work it out as Super Mario All-Stars had just come out. I'm certain he lost part of his IQ along the way and missed out on student debts and pressure. And he also lost me as a girlfriend. Actually, some will say things worked out for him quite nicely.

The pink menace to our daughters

A tsunami of sarcasm lies underneath the Amazon product page for Bic Crystal for Her, a set of pretty pens in pastel colours for delicate fillies like me, who can't use a macho normal black pen to write columns, lest my manicure ruptures and my ovaries hiss. The product reviews, left by spiky, hilariously strident feminists, are worth a 10-minute sitdown with a coffee. I wish I felt as sure that all this pink isn't what women actually, deep down want.

Lord knows, I tried with my books for young adults to make the covers ballsy, in neutral colours, without glitter and girly faff. I banged the desk in marketing meetings like a less affable Andrea Dworkin and demanded that young girls weren't demeaned. Then I'd speak at events and see girls float across with moonpie eyes to the books I'd permitted to be pink with a picture of a tiara, saying "Muuuuumy, this one!" Ever the put-upon-Pankhurst, I've cajoled my niece from a baby to see herself as equal, assertive and able to do anything a man does. A trip to a toy shop at the weekend saw her comb every inch of the shopfloor and choose a Pink Mini Hetty Hoover. "Why do you want a pink hoover?" I moaned. "It's pink and I can pretend to tidy up." You can't leave Amazon comments under children, but my thoughts were as black as tar.

twitter.com/@gracedent