Behaviorally, cats may lose interest in playing and become unhappy. At the same time, there may be excessive licking or stopping of grooming. The frequency of licking may increase, resulting in less and less hair, and even bald spots in some places.

In addition, cats may have reduced energy, become fatigued easily, feel listless, and may experience symptoms of lethargy or insomnia. Some cats may also experience psychomotor retardation or agitation, as well as loss of confidence and sensitivity to external factors.