Khat (also known as qat and kat) is a natural stimulant slow-growing shrub originally cultivated in East Africa and the Arabian Peninsula1. Its fresh leaves are crimson-brown of Catha edulis that emit a strong smell; it contains psychoactive ingredients that mediate its sympathomimetic effects known as cathinone (structurally and chemically similar to d-amphetamine) and cathine (a milder form that contain d-norisoephedrine)2,3. These substances release serotonin and dopamine in central nervous system and noradrenaline from peripheral sympathetic neurons4. On chewing khat leaves, these amphetamine-like constituents are released and produce excitation and increased motor activity, producing a feeling of exaltations, extreme loquacity, inane laughing. It is also an effective anorectic and results in constipation, dilate pupils, increase in heart rate and blood pressure which reflect its sympathomimetic effects5. Cathine is one of the alkaloids found in ephedra vulgaris, and fortunately khat is very rich in ascorbic acid, which is antidote to amphetamine–like compounds.
Khat is chewed by a large proportion of the adult population of the Yemen. It is estimated that up to 90% of adult males chew khat three to four hours daily, and the number for females may be as high as 50% or even higher 6 , and the practice of its chewing has been a part of the culture in areas of East Africa and throughout Saharan and sub-Saharan Africa since 7th century1. Its use has also spread to the immigrant Yemeni and Somali communities across Europe and America.
In Southern Arabia and Eastern Africa, Khat is traded openly and it is widely used across a range of age and class groups, and it is considered an integral part of cultural and social identity1. However; approval is not universal and it poses a public health problem and there is an awareness of the harmful effects on health and negative impact on productivity7.
Khat has deleterious effects on the central nervous system, cardiovascular, digestive and genitourinary systems, oral-dental tissues, diabetes mellitus and cancer8-10.
The neuropsychiatric consequences of Khat chewing were recognized in many case reports that implicated it in memory impairment, depression and psychoses11, and it can result in functional mood disorders12. Khat can also affect sleep, leading to rebound effects such as late awakening, decreased productivity and day-time sleepiness6. Moreover; Oyungu et al.13 demonstrated that khat may lower seizure threshold in their experiment on Sprague dawley rats. The World Health Organization classifies khat as causing psychological, but not physical dependence11.
Dystonia and dyskinesias can also be induced by qat as amphetamine-containing compounds are known inducer for movement disorders14. In our practice, there is mounting evidence that could suggest a causal relationship between qat and development of oromandibular dystonia (OMD). In our work on the effects of Botulinum toxin – type A (BTX-A) injection on OMD; one of the most outstanding feature in 5 of our patients with presumed secondary etiology was chronic Khat chewing. Those patients had otherwise normal neurological examination and normal brain MRI without any other apparent cause; those patients were from Yemen, and they considered khat chewing as a deep-rooted sociocultural tradition without perceiving it as “addictive drug”, they reported that, there is no social event [in Yemen] without khat; and one of the main challenges in quitting khat is finding alternatives to fill the void that would be left. The relation between khat chewing and oromandibular dyskinesia and dystonia was rarely addressed; however, Harms et al.15 proposed this relationship; and to our knowledge, there were no other studies that could recognize it as a causal factor. In 1994; Thiel and Dressler14 reported cases of previously healthy patients who developed persistent dyskinetic syndromes (spasmodic torticollis and cranial dystonia) following the intake of appetite suppressant that contains norpseudoephedrine (NPE), which is pharmacologically related to amphetamine.
Beside the chemical related effects of qat, we proposed mechanical effect as qat chewing or (better replaced by the Arabic word "takhzeen al-qat", which implicates chewing and storing of qat for several hours) 16 could be considered as task-specific dystonia similar to writers’ cramps.
Other important issue is related to chronicity of qat chewing; as chronicity implies both frequency and duration of chewing16; and some individuals may use it for many years but in a very low frequency (even once per month). Though recent reports strongly correlated the effects of this habit with the frequency; yet, this relationship to development of dystonia is questionable.
In the end, we must acknowledge that we know very little about the plausible role of qat in developing OMD and there is a great need for improved research on khat use and its possible association with OMD.
[Disclosure: Authors report no conflicts of interest]
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