What is the primary characteristic of tardive dyskinesia?

The primary characteristic of tardive dyskinesia is the presence of bizarre facial and tongue movements. This condition is often a result of long-term use of certain antipsychotic medications, which can lead to abnormal involuntary movements in the face, tongue, and other parts of the body. These movements can include lip smacking, grimacing, and other repetitive motion patterns that can be distressing to the individual and may affect their ability to speak or eat properly. The distinctive nature of these movements is what primarily defines tardive dyskinesia and distinguishes it from other side effects or psychiatric conditions.

The other options describe symptoms of different conditions or effects not specific to tardive dyskinesia. For instance, severe mood swings relate more to mood disorders, loss of appetite can occur in various medical conditions and psychiatric disorders, and excessive sleepiness may be associated with side effects from sedative medications or various health issues, but none of these are characteristic of tardive dyskinesia.