Hi lookout, many people have smoked the old style cannabis, still the common cannabis of the mid 80s for much longer than Jeremy Bamber had with absolutely no ill effects.
It's the hybrid strains of home grown cannabis introduced to the market long after 1985 which are the culprits of brain damage and psychosis, this is now the common cannabis sold on the streets.
Yes,Maggie,,,the " old style " cannabis was even given on prescription by two GP's that I knew,,,less harmful than tobacco and as a painkiller for joint pain. It was quite harmless in comparison to the stuff nowadays.