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NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

group is (-)cathinone, the active ingredient in freshly gathered leaves of the
Khat shrub (Catha edulis), whose actions are very similar to that of
amphetamine (Jaffe, 1990) (see Box 4.5). Amphetamines are used not only for
the subjective “high” that they produce, but also to extend periods of
wakefulness, as used by lorry drivers and students studying for exams. In
addition, they are used as appetite suppressants, although this effect is short-
lived. Medically, amphetamines are currently used only in the treatment of
narcolepsy, and in treating the symptoms of attention deficit hyperactivity
disorder (ADHD) in children. This condition is thought to be partly due to low
cortical norepinephrine, which permits subcortical emotional systems to
govern behaviour impulsively. When cortical arousal is facilitated with
psychostimulants, children with ADHD are able to pay attention to the tasks
they are engaged in (Panksepp, 1998) (see Box 4.6). Non-medical use of amphe-
tamines and related stimulants is a growing problem worldwide (see Box 4.7).

Behavioural effects
Amphetamines are stimulants of the central nervous system that produce
increased alertness, arousal, energy, motor and speech activity, increased self-
confidence and ability to concentrate, an overall feeling of well-being and
reduced hunger (Jacobs & Fehr, 1987; Hoffman & Lefkowitz, 1990). The short-
term effects of low doses of amphetamine include restlessness, dizziness,
insomnia, euphoria, mild confusion, tremor, and may induce panic or
psychotic episodes. There is a general increase in alertness, energy and activity,
and a reduction of fatigue and drowsiness. There may be heart palpitations,
irregular heartbeat, increased respiration, dry mouth and suppression of
appetite. With higher doses, these effects are intensified, leading to exhilaration
and euphoria, rapid flow of ideas, feelings of increased mental and physical
ability, excitation, agitation, fever and sweating. Paranoid thinking, confusion
and hallucinations have been observed. Severe overdose may lead to high fever,
convulsions, coma, cerebral haemorrhage and death (Jacobs & Fehr, 1987).

BOX 4.5
Khat
The leaves and buds of an East African plant, Catha edulis, which are chewed or
brewed as a beverage. Used also in parts of the eastern Mediterranean and
North Africa, khat is a stimulant with effects similar to those of amphetamine –
the reason being that the main active ingredient in khat is cathinone, an
amphetamine-like substance. Consumption of khat produces euphoria and
increased alertness, although concentration and judgement are impaired. Heavy
use can result in dependence and physical and mental problems resembling
those produced by other stimulants.
Source: WHO, 1994.

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