It was a solid, credible study in England but it was one in which they gave the test subjects isolated THC, not whole weed. It did cause significantly more paranoiac episodes and hallucinations in the group who got the THC, but scientists have known for a long while that in some susceptible groups, THC can bring out those symptoms. It may or may not be that those symptoms would be destined to come out no matter what. The findings of the study were significant enough that they didn't continue giving the study participants the THC samples.
Doctors: Marijuana Triggers Psychosis, Study Used Brain Scans For First Time To Show Link Between Pot And Paranoia - CBS News

We've had lots of passionate objectors here swearing that this is impossible, that it's baloney. But it's not. It's a very real finding. I keep preaching here that if we're ever going to do justice to cannabis, we'll have to accept the good with the bad. And this is further evidence that for some sensitive people, THC can cause schizophrenic reactions. For many more, it's fine. Just make sure you're smart enough to accept that, like with any other drug or even with certain foods, some people will have negative reactions. The smarter you are, the more easily you'll be able to see that cannabis isn't an all-or-nothing, good-vs.-bad issue. For some it's good. For others, it's not a beneficial substance.

420marijuana420, from a scientific standpoint, your poll above is a completely separate issue from the British study. You understand that, right? You're asking this population, which is a group that mostly smokes or somehow otherwise uses whole cannabis. And you're asking them for their personal experiences. The answers you get here won't affect the results of the British study, and you're only asking for anecdotal results. Just be aware that with the questions you've asked above and the group you're questioning here, you're not even remotely going to be able to prove or disprove the credibility of the British study.