Cannabis is so much stronger than it was in the sixties?
Short answer is: No, cannabis is not so much stronger than it was in the sixties.

How do I know? Easy, I was there then and I’m here now. I started smoking cannabis on April 20th 1968 when I was sixteen. They say that if you remember the sixties then you weren’t there, so how come I can remember the exact date on which I smoked my first joint?
Easy – there was a gig starring Geno Washington and the Ram Jam band in the Glen Ballroom in Llanelli then – I found the exact date on the Internet. That’s the night I inhaled for the first time. It was a tiny bit of hash I bought for a few shillings and it had no effect whatsoever on me,
The next day I went for a walk in the countryside near my home and smoked the other half of my stash. Minutes later I was dancing through the damp fields like a demented hippy, smiling and laughing at the beautiful planet I was privileged enough to live on.
Over the next three and a half years I smoked a lot more dope and had my share of most of the other drugs that were available, and there were a lot, even in our town in the sticks. For a few months during that period I shared a flat in London with a bunch of blokes, mostly from Llanelli. Early December 1969, we bought a large bag of what we were told was Mexican Grass.
There followed three weeks of mayhem, when I often forgot who I was, where I was and even what I was. Time chopped itself into short sequences and rearranged itself so that the thing I’ll be doing 5 minutes ago came after the thing that I was doing in half an hour’s time. I was reduced to my essential essence of being a consciousness floating in the continuum of space-time loosely connected to a seventeen year old boy from Wales.
This hallucinatory surreal journey continued until Christmas Eve when most of the Llanelli contingent hopped into a hired transit and belted off down the M4 to reconnect with our roots and reassemble our splintered brains. As it turned out I didn’t go back to London after that. When the transit came to pick me up the day after Boxing Day I was too exhausted after the grass and a bit ill after Christmas over-consumption. Just over two years later I was married with a child.
I stopped taking any kind of drug, even laid off alcohol for a few years and didn’t have another spliff for more than a quarter of a century. By then the good quality hash and grass of the late sixties had turned into impure and probably toxic ‘soap’ and ‘slate’ – concoctions of cannabis resin and god knows what bulking agents,
Gradually better quality weed came on the market – mostly strains of skunk grown in someone’s attic in small batches. The quality of the drug continued to improve and become more pure. I continued to smoke, and later vape, on and off, until quite recently, and I can vouch that nothing comes close to the strength and effects of that innocent sounding Mexican Grass that altered the course of my life in 1969.