However, the Zen master Hakuin worried about the practitioner who did too much mediation and suffered from a nervous breakdown (decrease in positive activity of the brain), and gave the secret of Naikan as a method of healing.
とはいえ参禅が限度を超えて神経衰弱の苦しみにある修行者を見かねた白隠禅師が、その治療方法としての内観の秘法を伝授した。