[pocoloco]

... the survey respondents didn’t necessarily perceive every non-euphoric event as negative. In fact [the study authors] deliberately avoided the word “adverse” in their study for this reason. Instead, they chose “challenging,” which better captured the meditators’ varied interpretations of their experiences.

I've meditated and attended multiple 10 day meditation retreats and I can attest that yes there are challenging moments and I have yet to experience an "adverse" event.

I would not say that meditation has a dark side. I would say that the meditators' minds are being stressed and challenged to the point where these react with such a force for which they were unprepared due to many reasons such as environment, emotional state, health issues, memories, etc. Like any activity, your mileage may vary.

I personally like to make that analogy of the mind to an OS which is trying to help you, an organism living in a giving environment, to identify and classify the stimuli it receives and generate an appropriate response. These responses are like programs that the mind/OS has generated to deal with the stimulus. All this is mechanical/automatic. If my limited understanding is correct, then meditation helps control this process and the process becomes less automatic and more controlled. The mind becomes more calmed and ready to focus on what you choose instead of whatever the stimuli dictates. Little by little the subconscious becomes conscious.

[FrozenVoid]

No. Meditations is like switching off internal firewalls(reality models) and trying to read raw packets(thought objects) on an ancient OS you only know by interface. You don't control the packets coming out, but you can apply filters and examine their structure. As you try to peek inside the system, it starts to behave weird as if it has more and more firewalls keeping secrets from you and when you break them down you lose protection from outside hackers and have to build up defenses from scratch.