Click to watch Dr. Willoughby Britton talk to the Dalai Lama about her research on the negative effects of meditation. He responds that problems can occur when the practice is decontextualized and is not grounded in tradition, knowledge, ethics, and morality.
So often today we see people blithely stripping off the practice from its tradition and using meditation for be-here-now, anything-goes, feel-good benefits while not including important components such as ethics and ignoring context. The Dalai Lama told the story of being shown the blueprints for a new meditation center. He looked them over and said, "Where's the library?" Knowledge of the tradition, and of the roots and principles of mediation, is critically important.
On a related note, click to read what Alan Wallace says about mindfulness minus its ethics.
What are some of the pitfalls of viewing meditation simply as a process of bare attention? When mindfulness is equated with bare attention, it can easily lead to the misconception that the cultivation of mindfulness has nothing to do with ethics or with the cultivation of wholesome states of mind and the attenuation of unwholesome states. Nothing could be further from the truth. In the Pali Abhidhamma, where mindfulness is listed as a wholesome mental factor, it is not depicted as bare attention, but as a mental factor that clearly distinguishes wholesome from unwholesome mental states and behavior. And it is used to support wholesome states and counteract unwholesome states.