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6. CONCURRENT DISORDERS

BOX 6.1

Substance use and the development of antisocial personality
disorder (ASPD)
Adolescents with depression often develop substance use disorders (SUD),
probably through efforts at self-medication. Substance use effects such as
impulsivity and aggressive or irresponsible behaviours, and substance use
consequences such as failure at school, and impairment of social functioning,
and the subsequent exposure to antisocial models of social cognition and
behaviour, may contribute to the development of antisocial personality disorder
(ASPD). Substance use may be the major mediator between depression and
ASPD during adolescence and young adulthood.
Recent research showed some evidence that SUD is a correlate of major
depressive disorders in adolescents and ASPD in young adults. Other correlates
may include poor social functioning or failure at school. Comparable correlates
support causal relationships between heterotypic disorders and, in the case of
ASPD, may provide useful leads for understanding the mechanisms involved in
the development of personality disorders.
Source: Chabrol & Armitage, 2002.

schizophrenia, while the rest start substance use around or after the first signs
of schizophrenia. In conclusion, although a clear association is indicated
between schizophrenia and depression, and substance dependence, there
are insufficient data to favour any specific hypothesis of shared neurobiology;
it is also possible that all three hypotheses are true. Future longitudinal
epidemiological studies are needed to directly address these questions.
An extension of the three hypotheses of shared neurobiology is that
substance dependence may involve, at least in some cases, self-medication
to reverse some of the neurotransmitter abnormalities associated with
depression or schizophrenia that either existed before or were induced by
substance use. None of the psychoactive substances are considered as
clinically effective antidepressant or antipsychotic medications by practising
clinicians. Nevertheless, the possibility remains that simultaneous or
sequential use of various substances – as “self-prescribed” by the emotional
or cognitive needs of the individual – leads to an adequate therapeutic effect
for specific symptoms, while the substance use may simultaneously worsen
other symptoms or the self-medicated symptoms in the long term. There are
indeed reports that substance dependence is associated with poorer outcome
and worse prognosis for patients with schizophrenia compared with patients
who are not users (Khantzian, 1985; Dixon, 1999). Thus, it may be possible
that psychoactive substances may provide short-term relief from some
symptoms but that the long-term outcome is worse than if the patient did
not use any drugs (Kosten & Ziedonis, 1997).

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