This new revised edition provides an updated workable base for the understanding of basic concepts of abnormal behaviour and abnormal psychology. Keeping in mind the latest developments in the field, it incorporates all the needed changes and modification in the book for meeting the requirement of the syllabi of the courses related to the subjects Abnormal and Clinical Psychology, in degree classes of the Universities and Higher Institutions of our country. The book is also helpful for those who opt Psychology as an optional paper for their Indian or Provincial Civil Services and other competitive examinations. Key Features: A through discussion on the concept, nature and background of abnormal behaviour and abnormal psychology by taking in to consideration different types of abnormalities and disorders of human behaviour along with their possible treatment measures; Adding four new chapters entitled as– Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism; Elimination and Eating Disorders; Sleep Disorders; Old Age or Degenerative Disorders; A through revision of the Chapter ‘Classification of Mental Disorders’ specifying a due place to the discussion of DSM IV-TR(2000), DSM-5 (2013), ICD-10 (2010), and a brief commentary on the coming ICD-11; Adding a number of useful topics in the existing chapters like Conflict resolution, Stressors, Stress cycle, Effects or Outcomes of Stress, New varieties of Obsessive-compulsive behaviour disorders (such as Hoarding disorder, Hair pulling disorder, Skin pulling disorder, and Body dysmorphic disorder), and Cognitive-behavioural therapy for the treatment of abnormal behaviour etc.