Shinzen Young, a Buddhist meditation teacher popular with young scientists, has summarized his familiarity with dark night experiences. In a 2011 email exchange between himself and a student, which he then posted on his blog,
http://shinzenyoung.blogspot.ru/2011_11_01_archive.html
Young presents an explanation of what he means by a "dark night" within the context of Buddhist experience:
Almost everyone who gets anywhere with meditation will pass through periods of negative emotion, confusion, [and] disorientation. …The same can happen in psychotherapy and other growth modalities. I would not refer to these types of experiences as 'dark night.' I would reserve the term for a somewhat rarer phenomenon. Within the Buddhist tradition, [this] is sometimes referred to as 'falling into the Pit of the Void.' It entails an authentic and irreversible insight into Emptiness and No Self. Instead of being empowering and fulfilling … it turns into the opposite. In a sense, it's Enlightenment's Evil Twin. This is serious but still manageable through intensive … guidance under a competent teacher. In some cases, it takes months or even years to fully metabolize, but in my experience the results are almost always highly positive.
Britton's findings corroborate many of Young's claims. Among the nearly 40 dark night subjects her team has formally interviewed over the past few years, she says most were "fairly out of commission, fairly impaired for between six months [and] more than 20 years."
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The Dark Night Project is young, and still very much in progress. Researchers in the field are just beginning to carefully collect and sort through the narratives of difficult meditation-related experiences. Britton has presented her findings at major Buddhist and scientific conferences, prominent retreat centers, and even to the Dalai Lama at the 24th Mind and Life Dialogue in 2012.