Avolition is a psychological state characterized by general lack of desire, motivation, and persistence. Commonly seen in patients with schizophrenia, those suffering from avolition will not start or complete any major tasks. This differs from anhedonia, where patients generally find task completion pleasureless.
It is the reduction, difficulty, or inability to initiate and/or persist in goal-directed behavior; it is quite often mistaken for apparent disinterest.
Avolition refers to the lack of initiative, or loss in drive and motivation to pursue realistic goals. Avolition is one of the four (affective flattening, alogia, anhedronia) main 'negative' symptoms of Schizophrenia. 
Characteristic symptoms are two (or more) of the following, each present for a significant portion of time during a 1-month period: delusions, hallucinations, disorganized speech (e.g., frequent derailment or incoherence), grossly disorganized or catatonic behavior, negative symptoms, i.e., affective flattening, alogia, or avolition. 
- Meadows G., Singh, B., & Griggs, M. (2007). 'Mental Health in Australia, Collaborative Community Practice 2nd Ed. Oxford University Press, Oxford. Chapter 25, p539.
- Hepatic insulin resistance in antipsychotic naive patients with schizophrenia, a detailed study of glucose metabolism with stable isotopes Lonneke J.M. van Nimwegen, MD1, Jitschak G. Storosum, MD, PhD2 , Regje M.E. Blumer, MD3, Gideon Allick, MD3 PhD, Henk W. Venema, PhD4, Lieuwe de Haan, MD, PhD1, Hiske Becker, MD1 , Therese van Amelsvoort, MD, PhD1, Mariette T. Ackermans, PhD 5 , Eric Fliers, MD, PhD3 , Mireille J.M. Serlie3, MD, Hans P. Sauerwein, MD PhD3 Dept of Psychiatry, Adolescent Clinic, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands 1 Dept of Psychiatry, SPDC, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands 2 Dept of Endocrinology and MetabolismCopyright (C) 2007 by The Endocrine Society Published in J Clin Endocrin Metab, 2007