I really wish that both good and bad trip reports would be much more thorough in their reporting.

Useful things to know to make sense of and draw useful conclusions from trip reports:

0 - whether there was any preparation (things like fasting, meditation, therapy, prayer, "clearing the space", etc)

1 - exactly what was taken and its purity, how the users knew they got the substance they were told they had, and whether they mixed drugs

2 - the dosage

3 - where they had the experience (whether it was done at a club, at a party, at a concert, in a city street, over dinner with one's parents, in nature, in therapy, at a friend's house, in a church, or in a shamanic ceremony will make a huge difference)

4 - who was with them (and whether these people were trained or at least experienced in guiding psychedelic trips)

5 - whether they had set any concrete, constructive intentions beforehand, or whether it was done on a whim, to "party" or to "get fucked up"

6 - what was their mindset and life circumstances beforehand (tired? depressed? anxious? struggling with a breakup, a divorce, or a death of a loved one? a history of abuse or trauma in their past?)

7 - how much they themselves had researched about what they were getting themselves in to, and in to mystical, psychedelic, shamanic, and non-ordinary states of consciousness in general and how different cultures and peoples have dealt with and made sense of them

8 - whether they used any strategies before or during the session to prevent or handle adverse effects (things such as ritual, dance or movement, chanting, singing, playing musical instruments, prayer or calling for help from their guides, friends, god(s), or their own inner source of strength or wisdom)

9 - whether and what kind of music was played during the experience (a well designed musical accompaniment can make a huge difference, and this is one of the critical means by which the MAPS psilocybin and MDMA studies maximized the chances of having a constructive experience)

10 - how or if they tried to integrate the experience afterwards

11 - whether they consulted therapists specializing in psychedelic integration afterwards

12 - whether they themselves or anyone in their family had a history of mental illness

13 - how much prior experience with psychedelics they had, and which psychedelics they had used

14 - whether they were on any psychoactive medications

15 - what their state of physical health was

This is a lot to ask for, but without such details it's really hard to draw conclusions.

That said, yes, it's possible to have really harrowing experiences, and some people come out scarred from them, having gotten nothing positive from the experience at all.

But it is possible to prepare for psychedelic experiences in such a way as to minimize the risk of negative experiences, and if such experiences do happen to deal in constructive ways with them both during and after.

Unfortunately, many people don't know how to do that, or choose not to.

Something else to think about: Some people think they're "happy" or "normal", but they're really not, and just haven't been able to face their own dark sides, repressed past traumas, or the difficulties they have relating with others, and these things can come up during the trip or influence it.

Then a common reaction is to fight these realizations or run away from them, to hold on tight and not let go, which all but guarantees a difficult experience. In contrast, the MAPS guidelines advise to squarely face the difficulties (including physical difficulties like pain or discomfort, and even annoyance at the music), to explore them, to not fight them, and to surrender and let go. That tends to lead to a freeing, blissful, constructive experience.

One final thing: In an interview I once heard with a veteran psychedelic therapist, who'd overseen hundreds of psychedelics sessions, he said the people who had the toughest times with these substances were die hard theists or atheists with something to prove, because they both went in to the experience with an attitude of "I know what's going on!" They weren't able to just go with whatever was revealed to them.