Animal studies across several species demonstrate that high dosages of methamphetamine damage nerve cells (Swan, 1997). In rats, one high dose is enough to cause damage to neurons; prolonged administration increases the number of neurons that are killed o (Swan, 1997). Twelve to eighteen months aer exposure, serotonin-producing nerves grow abnormally or not at all. Buenstein, Coel, and Combs (1997) showed through single photon emission computed tomography (SPECT) scanning of methamphetamine abusers in Hawaii that brain deterioration continues for months aer abstinence, a nding that, if consistently cross-validated, suggests another unique and pathological feature of methamphetamine (see Chapter 3, Figure 3.1).