BACKGROUND:
Sexual
offending is a serious social problem, a public health issue, and a major
challenge for social policy. Victim surveys indicate high incidence and
prevalence levels and it is accepted that there is a high proportion of hidden
sexual victimisation. Surveys report high levels of psychiatric morbidity in
survivors of sexual offences.Biological treatments of sex offenders include
antilibidinal medication, comprising hormonal drugs that have a
testosterone-suppressing effect, and non-hormonal drugs that affect libido
through other mechanisms. The three main classes of testosterone-suppressing
drugs in current use are progestogens, antiandrogens, and
gonadotropin-releasing hormone (GnRH) analogues. Medications that affect libido
through other means include antipsychotics and serotonergic antidepressants
(SSRIs).
OBJECTIVES:
To
evaluate the effects of pharmacological interventions on target sexual
behaviour for people who have been convicted or are at risk of sexual offending.
SEARCH METHODS:
We
searched CENTRAL (2014, Issue 7), Ovid MEDLINE, EMBASE, and 15 other databases
in July 2014. We also searched two trials registers and requested details of
unidentified, unpublished, or ongoing studies from investigators and other
experts.
SELECTION CRITERIA:
Prospective
controlled trials of antilibidinal medications taken by individuals for the
purpose of preventing sexual offences, where the comparator group received a
placebo, no treatment, or 'standard care', including psychological treatment.
DATA COLLECTION AND ANALYSIS:
Pairs
of authors, working independently, selected studies, extracted data, and
assessed the risk of bias of included studies. We contacted study authors for
additional information, including details of methods and outcome data.
MAIN RESULTS:
We
included seven studies with a total of 138 participants, with data available
for 123. Sample sizes ranged from 9 to 37. Judgements for categories of risk of
bias varied: concerns were greatest regarding allocation concealment, blinding
of outcome assessors, and incomplete outcome data (dropout rates in the five
community-based studies ranged from 3% to 54% and results were usually analysed
on a per protocol basis).Participant characteristics in the seven studies were
heterogeneous, but the vast majority had convictions for sexual offences,
ranging from exhibitionism to rape and child molestation.Six studies examined
the effectiveness of three testosterone-suppressing drugs: cyproterone acetate
(CPA), ethinyl oestradiol (EO), and medroxyprogesterone acetate (MPA); a
seventh evaluated two antipsychotics (benperidol and chlorpromazine). Five
studies were placebo-controlled; in two, MPA was administered as an adjunctive
treatment to a psychological therapy (assertiveness training or imaginal
desensitisation). Meta-analysis was not possible due to heterogeneity of
interventions, comparators, study designs, and other issues. The quality of the
evidence overall was poor. In addition to methodological issues, much evidence
was indirect.
PRIMARY OUTCOME:
recividism.
Two studies reported recidivism rates formally. One trial of intramuscular MPA
plus imaginal desensitisation (ID) found no reports of recividism at two-year
follow-up for the intervention group (n = 10 versus one relapse within the
group treated by ID alone). A three-armed trial of oral MPA, alone or in
combination with psychological treatment, reported a 20% rate of recidivism
amongst those in the combined treatment arm (n = 15) and 50% of those in the
psychological treatment only group (n = 12). Notably, all those in the 'oral
MPA only' arm of this study (n = 5) dropped out immediately, despite treatment
being court mandated.Two studies did not report recidivism rates as they both
took place in one secure psychiatric facility from which no participant was
discharged during the study, whilst another three studies did not appear
directly to measure recividism but rather abnormal sexual activity alone.
SECONDARY OUTCOMES:
The
included studies report a variety of secondary outcomes. Results suggest that
the frequency of self reported deviant sexual fantasies may be reduced by
testosterone-suppressing drugs, but not the deviancy itself (three studies).
Where measured, hormonal levels, particularly levels of testosterone, tended to
correlate with measures of sexual activity and with anxiety (two studies). One
study measured anxiety formally; one study measured anger or aggression.
Adverse events: Six studies provided information on adverse events. No study
tested the effects of testosterone-suppressing drugs beyond six to eight months
and the cross-over design of some studies may obscure matters (given the
'rebound effect' of some hormonal treatments). Considerable weight gain was
reported in two trials of oral MPA and CPA. Side effects of intramuscular MPA
led to discontinuation in some participants after three to five injections (the
nature of these side effects was not described). Notable increases in
depression and excess salivation were reported in one trial of oral MPA. The
most severe side effects (extra-pyramidal movement disorders and drowsiness)
were reported in a trial of antipsychotic medication for the 12 participants in
the study. No deaths or suicide attempts were reported in any study. The latter
is important given the association between antilibidinal hormonal medication
and mood changes.
AUTHORS' CONCLUSIONS:
We
found only seven small trials (all published more than 20 years ago) that
examined the effects of a limited number of drugs. Investigators reported
issues around acceptance and adherence to treatment. We found no studies of the
newer drugs currently in use, particularly SSRIs or GnRH analogues. Although
there were some encouraging findings in this review, their limitations do not
allow firm conclusions to be drawn regarding pharmacological intervention as an
effective intervention for reducing sexual offending.The tolerability, even of
the testosterone-suppressing drugs, was uncertain given that all studies were
small (and therefore underpowered to assess adverse effects) and of limited
duration, which is not consistent with current routine clinical practice.
Further research is required before it is demonstrated that their
administration reduces sexual recidivism and that tolerability is maintained.It
is a concern that, despite treatment being mandated in many jurisdictions,
evidence for the effectiveness of pharmacological interventions is so sparse
and that no RCTs appear to have been published in two decades. New studies are
therefore needed and should include trials with larger sample sizes, of longer
duration, evaluating newer medications, and with results stratified according
to category of sexual offenders. It is important that data are collected on the
characteristics of those who refuse and those who drop out, as well as those
who complete treatment.
- 1The Priory Group, Chadwick Lodge, Chadwick Drive, Eaglestone, Milton Keynes, Buckinghamshire, UK, MK6 5LS.
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