Lachkar's main focus is the relationship between someone with narcissistic personality disorder and someone with a borderline personality disorder. Her first book on the subject was The Narcissistic/Borderline Couple: A Psychoanalytic Perspective on Marital Treatment, in which she explores how partners form a parasitic bond and play out a drama of earlier conflictual experiences, characterized by their painful, circular patterns of behaviour. In the second edition, The Narcissistic/Borderline Couple: New Approaches to Marital Therapy, Lachkar ventures to go beyond narcissistic and borderline couples to a mélange of many other dyadic configurations. She explains how each partner stirs some unresolved issue in the other and how each one identifies or over-identifies with the negative projections to the other. To describe this process, she coined term "dual projective identification", which is an expansion on Melanie Klein's projective identification. Lachkar's publications on the relationship between a narcissistic and a borderline led her to analyze the differences in communicating with each. This analysis was expressed in her most recent work, How to Talk to a Narcissist, and How to Talk to a Borderline, in which she also describes eight different types of narcissists and eight different types of borderlines. In these last two books, Lachkar elaborated on Marsha M. Linehan's work with Dialectical Behavioral Therapy by developing the "Language of Dialectics," which is a concept used in the communication with various types of borderlines. Parallel to this notion, Lachkar employed Heinz Kohut's work on self psychology to develop the "Language of Empathology," which is used in communicating with different types of narcissists.
Emotional abuse
Dr. Lachkar has also published a few books focusing on the treatment of emotional abuse. She examined the origins and early warning signs of the psychological violation, introduced the typologies of the abuser and the abused, and explored the bases for their collusive attachments in The Many Faces of Abuse: Treating the Emotional Abuse of High -Functioning Women. In The V-Spot: Healing the Vulnerable Spot from Emotional Abuse, Lachkar explores the healing process of the most sensitive area of emotional vulnerability.