a neurological disorder. However, because the voice can sound normal or near normal at times, some practitioners believe it to be psychogenic; that is, originating in the affected person's mind rather than from a physical cause. This was especially true in the 19th and 20th centuries. No medical organizations or groups take this position. A comparison of SD patients compared with vocal fold paralysis (VFP) patients found that 41.7% of the SD patients met the DSM-IV criteria for psychiatric comorbidity compared with 19.5% of the VFP group. However, another study found the opposite, with SD patients having significantly less psychiatric comorbidity compared to VFP patients: "The prevalence of major psychiatric cases varied considerably among the groups, from a low of seven percent (1/14) for spasmodic dysphonia, to 29.4 percent (5/17) for functional dysphonia, to a high of 63.6 percent (7/11) for vocal cord paralysis." A review in the journal Swiss Medicine Weekly states that "Psychogenic causes, a 'psychological disequilibrium', and an increased tension of the laryngeal muscles are presumed to be one end of the spectrum of possible factors leading to the development of the disorder". Alternatively, many investigations into the condition feel that the psychiatric comorbidity associated with voice disorders is a result of the social isolation and anxiety that patients with these conditions feel as a consequence of their difficulty with speech, as opposed to the cause of their dysphonia. The opinion that SD is psychogenic is not upheld by experts in the scientific community. SD is formally classified as a movement disorder; it is a type of focal dystonia known as laryngeal dystonia. Diagnosis Diagnosis of spasmodic dysphonia requires a multidisciplinary team and consideration of both perceptual and physiological factors. There is currently no universally accepted diagnostic test for spasmodic dysphonia, which presents a challenge for diagnosis. Additionally, diagnostic criteria have not been agreed upon as the distinguishing features of this disorder have not been well-characterized. A team of professionals including a speech-language pathologist, an otolaryngologist, and a neurologist, are typically involved in spasmodic dysphonia assessment and diagnosis. The speech-language pathologist conducts a speech assessment including case history questions to gather information about voice use and symptoms. This is followed by clinical observation and perceptual rating of voice characteristics such as voice breaks or strain, which are selectively present in normal speech over other voice activities such as whispering or laughing. Symptoms also vary across types of