Nidotherapy is a new form of psychological therapy that aims to improve mental health by a systematic and collaborative manipulation of the environment in all its forms without focusing on alleviation of symptoms. Following treatment with nidotherapy, we describe a dramatic, and continuing, improvement in a woman with comorbid severe depressive illness and borderline personality disorder. She had made repeated serious suicide attempts over the previous 25 years and had received many drug and psychological treatments without success. The nidotherapy solution enabled her to leave home and achieve greater autonomy. Prior to this, she had been demeaned and undermined in her role as a family carer, and no health professionals had appreciated previously the restrictions it had placed on her health and well-being. Nidotherapy effected a smooth and orderly transition with family approval; the reasons for this seem to lie in the emotional neutrality of nidotherapy as a purely environmental intervention. Without this approach, we judge that separation from the family would not have been possible. Copyright © 2017 John Wiley & Sons, Ltd.