Recruitment and procedure

The participants were recruited from local mental health services in Birmingham and Solihull, Sandwell and a West Midlands semi-secure unit for offenders with mental illness. Inclusion criteria were that patients conformed to an ICD–10 diagnosis of schizophrenia or related disorder with command hallucinations for at least 6 months (World Health Organization, 1992). Participants were required to have a recent history of compliance with, and appeasement of, voices with ‘severe’ commands, including harm to self, others or major social transgressions. Patients were excluded if they had a primary organic or addictive disorder.

All aspects of recruitment, screening and outcome assessment were organised and administered by an experienced research associate (A.N.) between September 2000 and July 2002. All patients referred were offered an interview to establish eligibility and to obtain consent, and a further interview for eligible patients for assessment with the outcome measures (see below). Eligible and consenting patients were then randomly assigned to CTCH or TAU by means of a computerised random number generator administered by the Birmingham Clinical Trials Unit independent of the research team, to ensure the research associate was blind to the allocation at baseline and post-testing. Participants were post-tested at 6 months after CTCH or TAU and again at 12 months’ follow-up.

Power calculations were based on previous cognitive therapy trials which suggest a relatively large effect size of 0.65 post treatment and 0.93 at 12 months’ follow-up (Reference Gould, Mueser and BoltonGould et al, 2001; Reference Cormac, Jones and CampbellCormac et al, 2002); predicting a reduction from 95% with at least partial compliance to 50% would require a sample size of 23 in each of two groups to achieve a power of 0.9 with alpha=0.05.

Measures

Measures of cognitions and behaviours, symptoms and affect relevant to the hypotheses were given at pre-test, post-test and follow-up. The cognitive and behavioural measures were as follows.

Treatment groups

Consenting participants were assigned randomly to either TAU or CTCH plus TAU for a period of 6 months. The research associate responsible for outcome evaluation was blind to group allocation (A.N.) and participants were instructed not to disclose their allocation.

TAU

This was delivered by community mental health teams. A detailed breakdown of the services received by the control and treatment groups during the trial and 1 year before the trial are shown in Table 1. This shows that TAU was extensive, involving 18 categories of service and admissions.

Table 1 Service consumption before and during the trial: proportion of patients using services, categorised by treatment group

	Year before trial		During trial
	TAU %	CTCH %	TAU %	CTCH %
Services
Out-patients	85	89	100	89
CPN	50	33	60	56
Day centre	45	38	35	28
Social worker	0	22	25	11
Supported accommodation	30	22	55	28
Support worker	25	50	45	11
Community drug team	5	6	5	0
Probation officer	5	6	5	6
Occupational therapist	35	22	20	11
Psychologist	151	161	52	62
Respite care	0	6	5	6
Home treatment team	22	6	20	6
Art therapy	10	6	5	0
Voices group	0	6	0	0
ECT	0	0	0	6
Admissions
Informal	20	22	15	22
Section 2	10	0	5	6
Section 3	15	0	15	0
Guardianship Order	0	6	0	6

Medication was recorded 12 months before, and during, the trial.

Statistical analysis

Hypotheses were tested using the Generalized Linear Interactive Modelling Program (GLIM) in the Statistical Package for the Social Science for Windows, version 10. The statistical model was treatment group × time, with repeated measures on the time factor. The test of each hypothesis focused on the interaction term. It is also of interest to determine if there are general trends across time in both groups (e.g. reduction in compliance) tested using the ‘time’ main-effect term of the GLIM analysis.

To test whether the intervention was effective, baseline v. 6 months measures were used; for maintenance of any treatment effects, baseline v. 12 months measures were used. Exact probability values were calculated.

Description of the sample

A total of 224 referrals were screened, from which 69 patients were identified as being eligible for the study and were invited to participate. Of these, 31 refused consent, leaving a sample of 38 consenting to randomisation (Fig. 1). The sample included 24 men and 14 women, with a mean age of 35.5 years (s.d. 10.4). The sample was drawn from a broad ethnic base, including 27 (71%) White, 6 (16%) Black Caribbean and 4 (14%) other/South Asian patients. The clinical and demographic characteristics of the treatment and control groups are shown in Table 2. Those refusing consent did not differ from the participants on available data (gender, age, duration of illness).

Fig. 1 CONSORT diagram.

Table 2 Clinical and demographic characteristics of the treatment and control groups

	CTCH	TAU
Age, years
Mean (s.d.)	36.6 (10.3)	35.1 (10.4)
Range	17-56	19-60
Gender, n
Male	10	14
Female	8	6
Ethnicity, n
White	13	14
Black	4	3
Asian	1	1
Other	0	2
Diagnosis, n
Schizoaffective	4	0
Schizophrenia	6	11
Paranoid schizophrenia	5	5
Personality disorder	1	2
Psychotic depression	1	2
OCD	1	0
PANSS score
Positive scale
Mean (s.d.)	21.9 (3.1)	20.8 (3.2)
Range	16-28	16-28
Negative scale
Mean (s.d.)	20.8 (6.4)	21.5 (6.4)
Range	12-34	13-34
General psychopathology
Mean (s.d.)	36.3 (6.6)	35.9 (6.7)
Range	26-47	28-49
Duration of voices, years
Mean (s.d.)	13.4 (9.9)	10 (5.7)
Duration of commands, years
Mean (s.d.)	8.8 (7.9)	8.6 (5.9)

Prescribed neuroleptic medication converted to CPZ equivalents is presented in Table 3. No difference was observed at baseline between the two groups (F 2.0, NS). At baseline, 13/18 (72%) in CTCH were prescribed atypicals, including 5 patients taking clozapine; in TAU, 13/20 were prescribed atypicals (65%), including 7 patients taking clozapine. A group × time repeated measure analysis of variance conducted on the drug data confirmed no overall difference between groups, but found a group × time interaction (F=6.3, P=0.005). Table 3 shows that this was due to a steady rise in prescribed neuroleptic drugs in the TAU group (t=3.0, P<0.01) and a small but significant decrease in the CTCH group (t=2.3, P<0.05). The numbers of participants receiving atypicals in either group were unchanged at follow-up.

Table 3 Changes in prescribed antipsychotic medication

	CTCH (n=17) Mean (s.d.)	TAU (n=16) Mean (s.d.)
Chlorpromazine equivalent, mg/day
Baseline	1181 (948)	779 (646)
6 months	1167 (958)	893 (601)
12 months	1127 (969)	1038 (657)

Types of commands, compliance and forensic history

All patients reported two or more commands from the ‘dominant’ voice, at least one of which was a ‘severe’ command. The most severe commands were to kill self (25), kill others (13), harm self (12) and harm others (14). Less severe commands involved innocuous, everyday behaviour (wash dishes, masturbate, take a bath) and minor social transgressions (e.g. break windows, shout out loud, swear in public). Further details, including incidence and examples of compliance and appeasement of such commands for the sample as a whole, are shown in Table 4.

Table 4 Prevalence of and types of commands, compliance and appeasement in the whole sample

Command and prevalence	Example	Compliance	Appeasement
Command to kill self (treatment n=12, control n=13)	‘Stab yourself’	Nine patients had previously attempted suicide. One patient committed suicide during the trial	Seven patients used appeasement behaviours including holding a knife to their wrist, taking razor blades into the bath, collecting tablets and planning and executing suicide in their imagination
	‘Slash your wrists’
	‘Overdose’
	‘Hang yourself’
	‘Gas yourself’
Command to kill others (treatment n=6; control n=7)	‘Cut her throat’	Four patients in the sample had attempted to kill someone, either by suffocation, poisoning or physical assault with a hammer	Three patients used appeasement behaviours including arming themselves with knives, baseball bats and an axe and making guns out of tinfoil
	‘Go and kill someone’
	‘Kill the therapist’
	‘Kill your husband and daughter’
Command to harm self (treatment n=9; control n=3)	‘Burn yourself’	Nine patients had harmed themselves in response to commands. This included cutting, swallowing nail polish remover or bleach, jumping in front of cars, walking on glass and setting oneself alight	Three patients used appeasement behaviours including picking at previous wounds, and standing on the kerb
	‘Cut yourself’
	‘Set yourself alight’
	‘Pour hot water on yourself’
	‘Go into the road’
Command to harm others (treatment n=8; control n=6)	‘Touch your children’	Seven patients had harmed others in response to commands. This included hitting children, knocking them into furniture, scolding them, hitting people, attacking someone with a knife	Two patients used appeasement behaviours including hitting others with minimal force, and covert appeasement by thinking ‘I'll do that later’
	‘Kick them’
	‘Hit them’
	‘Beat that person up’
	‘Rape your neighbour’

Participants were considered at high risk of compliance because 30 (79%) had complied, 14 (37%) had appeased, and 29 (76%) had expressed the fear that the voices would either harm or kill them or a family member if they did not comply. The compliance rate is at the high end of the range for recent studies (Sawyer et al, 2003), because our sampling strategy involved identifying those considered to have recently complied.

Five participants in the sample had been prosecuted or cautioned for behaviour linked to voices’ commands. This included causing actual bodily harm to a minor, grievous bodily harm, theft and common assault. Three participants had been hospitalised (two detained under the Mental Health Act, 1983), for attempting to kill someone in response to voices within the last 3 years.

A further indication of the severity of need in this sample was the heavy and prolonged consumption of TAU, both during the trial and as sampled 1 year before the trial. TAU involved 17 categories of service and admissions, as shown in Table 1.

Another indication of severity was the fact that at the time of consent to enter the trial, eight patients were hospitalised; two admissions were under Section 3 and one under Section 2 of the Mental Health Act (1983), and another five were informal admissions.

Allocation and flow of participants

As shown in the CONSORT diagram (Fig. 1), 38 of 69 eligible participants were randomly allocated, 18 to CTCH and 20 to TAU. The CTCH and TAU groups did not significantly differ on any demographic, illness history or voice characteristics at baseline (see Table 2). The treatment group completed a median of 16 sessions. Five participants (27%) in the treatment group dropped out prematurely, attending between 4 and 12 sessions. This drop-out rate is comparable with other trials of this type (Reference Norman and TownsendNorman & Townsend, 1999; Reference Durham, Guthrie and MortonDurham et al, 2003). The intention was to include all 18 CTCH participants at follow-up, but at 6 months three participants were lost to follow-up through withdrawal of consent, and a further one at 12 months. In the control group, two were lost to follow-up at 6 months (both died; one death was due to natural causes and the other to suicide) and two were lost at 12 months. There was no difference between groups in number lost to follow-up.

The impact of CTCH

Compliance with commands

The CTCH and TAU groups did not differ in compliance with commands at baseline, as measured by the VCS. There was a general effect of time, with both groups showing a reduction in compliance (F=89.3, P<0.0001); however, this was marked in the CTCH group (F _interaction=4.8, P=0.036; Table 5). These treatment gains were maintained at 12 month follow-up (F _interaction=7.8, P<0.001). To gauge the comparative size of this effect, at 6 months 39% of the TAU group scored 4 or 5 on the compliance scale (partial or full compliance) compared with 14% of the CTCH group. This compares with a baseline figure of 100% for the CTCH and 94% for the TAU groups. The effect size of CTCH was 1.1.

Table 5 Mean scores (s.d.) on the Voice Compliance Scale showing impact of CTCH on compliance with commands

	CTCH	TAU
Baseline	4.7 (0.5)	4.8 (0.5)
Post-treatment	1.8 (1.2)	3.1 (1.4)
12 months	1.7 (1.1)	3.4 (1.6)

These findings were unaffected when change in neuroleptic dose over time was used as covariate. However, within the TAU group, the rise in neuroleptic dose was correlated (r=0.46, NS) with reducing compliance; and in the CTCH group, the reduction in medication use was correlated (r=0.63, P<0.01) with reducing compliance. At baseline and follow-up, there was no correlation between medication dose and compliance or voice power.

Beliefs about voices

Findings on the four main voice belief variables were as follows:

1. (a) Power (VPD). The CTCH group reported a large and significant reduction in the power of the dominant voice, compared with the TAU group, which showed no change (F _interaction=19.4, P<0.0001; Table 6). This effect of CTCH was maintained at 12 months follow-up (F _interaction=15.1, P<0.001).

2. (b) Malevolence (BAVQ). There was no impact of CTCH on the perceived malevolence of voices at 6 months (F _interaction<1, NS) or 12 months (F _interaction<1, NS).

3. (c) Omniscience (BAVQ). The belief in voices’ omniscience declined significantly in the CTCH group but not in the TAU group (F _interaction=3.9, P=0.05). This pattern was maintained at 12 months (F _interaction=6.3, P=0.02).

4. (d) Perceived control (PSYRATS). Patients receiving CTCH showed a significant improvement in perceived control over voices, compared with the TAU group, which showed no change (F _interaction=11.3, P=0.002). This pattern was maintained at 12 months (F _interaction=7.2, P=0.01).

Table 6 Mean scores (s.d.) showing impact of CTCH compared to TAU on measures of voice beliefs, topography and distress

	CTCH			TAU
	Baseline	6 months	12 months	Baseline	6 months	12 months
Voice power (VPD)	28.0 (4.7)	17.4 (6.7)	18.0 (6.5)	26.0 (7.8)	26.7 (5.3)	29.1 (6.2)
Malevolence (BAVQ)	23.2 (6.9)	18.3 (7.5)	21.7 (8.6)	19.6 (8.8)	19.8 (8.9)	20.7 (8.6)
Omniscience (BACQ)	11.4 (2.8)	9.1 (4.4)	9.1 (2.1)	9.8 (3.1)	10.2 (4.1)	10.0 (4.6)
Distress (PSYRATS)	3.4 (0.5)	2.2 (0.9)	2.7 (0.8)	3.2 (0.73)	2.9 (1.0)	3.0 (1.1)
Frequency (PSYRATS)	3.5 (0.5)	2.5 (1.0)	2.7 (1.3)	2.8 (1.1)	2.7 (1.1)	2.9 (1.0)
Loudness (PSYRATS)	2.6 (1.0)	2.0 (0.9)	2.6 (1.3)	2.2 (1.2)	2.4 (0.9)	2.3 (0.8)
Negative content (PSYRATS)	3.4 (0.6)	3.1 (1.1)	3.6 (0.7)	3.6 (0.5)	3.4 (0.8)	3.7 (0.6)
Control (PSYRATS)	3.7 (0.5)	2.7 (1.4)	2.6 (1.5)	3.4 (0.8)	3.6 (0.9)	3.6 (0.8)
Depression (CDSS)	9.7 (5.9)	8.0 (6.3)	8.1 (7.4)	8.9 (6.8)	9.3 (6.9)	12.6 (6.7)

Psychotic symptoms

Although change in psychotic symptoms was not predicted, a significant drop occurred in PANSS positive symptoms amounting to 3.7 points in the CTCH group, from a baseline of 21.8, and a small increase occurred in the control group (F _interaction=12.6, P<0.001). Similarly, there was a small but consistent reduction in negative symptoms (F _interaction=14.8, P=0.001) and general psychopathology (F _interaction= 18.8, P<0.001) in the CTCH group (Table 7). These effects were maintained at 12 months for positive symptoms (F _interaction= 14.2, P=0.001), negative symptoms (F _interaction=12.3, P=0.002) and general psychopathology (F _interaction=15.5, P=0.001).

Table 7 Correlations between voice compliance, distress, power and omniscience of disobedience

	Distress	Power	Omniscience
Voice compliance	0.38*	0.46**	0.32
Distress (PSYRATS)		0.55**	0.47**
Power differential (VPD)			0.37

Within the PANSS positive scale, hallucinations showed a non-significant reduction at 6 months (F=3.8, P=0.06); however, by 12 months, no difference between the groups was observed (F _interaction=1.46, NS). In contrast, for the delusions sub-scale there was a reduction in the CTCH group at 6 months (F _interaction=5.6, P=0.0025), sustained at 12 months (F _interaction=3.98, P=0.005).

Within the general psychopathology scale, there were significant changes in anxiety at 6 months (F _interaction=10.6, P=0.004) and 12 months (F _interaction=9.9, P=0.004); in tension at 6 months (F _interaction=5.1, P=0.03); and in guilty thinking at 6 months (F _interaction=4.6, P=0.042).

Within the negative symptoms scale, there was a significant reduction in attention/concentration at 6 months (F _interaction=13.2, P=0.001), and disturbance of volition at 6 months (F _interaction=6.2, P=0.019) and 12 months (F _interaction=15.5, P=0.001).

There was no correlation between neuroleptic dose and PANSS positive symptoms at any point.

Construct validity of the VCS

Social rank theory applied to the experience of voices argues that compliance with a powerful dominant (voice) will vary as a function of: the power differential between the dominant (voice) and subordinate (voice hearer); the distress or fear experienced; and the beliefs about non-compliance (see Reference GilbertGilbert, 1992).

We can put this critical aspect of our theory to the test. This will, in addition, serve to test the validity of the VCS if it correlates lawfully with these self-report scales.

The correlation matrix at 6 months (when the VCS has more variability) is shown in Table 7. Voice compliance was correlated significantly with both greater distress and power, with a trend for omniscience (multiple R=0.55, P<0.01).

Reduction in compliance

The data presented here suggest that CTCH, in the context of good quality and a high level of TAU services, exerts a major influence on the risk of compliance, reduces distress and prevents the escalation of depression, compared with TAU alone. Depression is known to be high in this group from previous research (Reference Birchwood, Meaden and TrowerBirchwood et al, 2000), confirmed in this study. Because of the selection criterion of recent compliance, it was likely that compliance behaviour would reduce over the 6-month and 12-month periods (‘regression to the mean’); however, given the high risk status of this group, we could expect an increasing number of people complying with commands as further time elapses. Nevertheless, the 12-month clinical impact of CTCH was significant. Perhaps more importantly, the risk factors for compliance in the CTCH group had reduced markedly, particularly the perceived power of the voice, its omniscience and controllability, and the need to appease it (14% of the CTCH group were appeasing or complying v. 53% of the TAU group).

Change in beliefs

In line with our prediction, neither the topography nor the negative content of voices shifted (according to the self-reports of participants on the PSYRATS), with the exception of a temporary reduction in perceived frequency during the first 6 months. This underlines our view (Reference Birchwood, Spencer, Maj and SartoriusBirchwood & Spencer, 2002) that cognitive–behavioural therapy (CBT) is most effective with beliefs (delusional or otherwise), rather than the primary psychotic experience, in this case auditory hallucinations. The focus of CTCH is to change fundamentally the nature of patients’ relationships with their voices by challenging the power and omnipotence of the voices, thus reducing the motivation to comply. However, if these treatment gains are sustained, the reduction of distress might well exert a beneficial influence on the frequency of voices. In a similar vein, we previously observed the similarity between the nature and content of voices and negative thoughts in depression (Reference Gilbert, Birchwood and GilbertGilbert et al, 2001); relieving depression in this sample could act to reduce the frequency and negative content of voices, although in the time scale observed here, only limited change was noted.

The reduction in PANSS positive symptoms was modest but consistent in the CTCH group, leading to a highly significant and sustained effect. The hallucinations sub-scale showed a non-significant decline over 6 months which disappeared at 12 months, once more underlining our contention that voice activity per se is not affected. The delusions sub-scale, in contrast, showed a significant reduction at 6 and 12 months. This could well reflect the observed changes in the perceived power of the persecutor, in this instance the voice. The PANSS general psychopathology score showed the largest and most sustained reduction, particularly social avoidance, attention and concentration.

Internal and external validity

Our primary dependent measure – compliance with commands – is not a straight-forward concept (Reference Beck-Sander, Birchwood and ChadwickBeck-Sander et al, 1997), as compliance can include both covert as well as overt acts, and patients can also appease their voices by complying with less serious commands (a ‘safety behaviour’). Our measure, developed from our earlier work (Reference Beck-Sander, Birchwood and ChadwickBeck-Sander et al, 1997), recognises these subtleties and requires evidence not only from the client, but also from relatives or case managers. The rating of this scale was undertaken by three raters in the first instance to establish interrater reliability.

We are encouraged that the study also found (predicted) changes in power, distress/depression and omniscience (which were largely measured by self-report scales) and that these correlated significantly with our primary outcome, compliance; indeed, when power was controlled for in an analysis of covariance, the effect on compliance was rendered non-significant. This adds strength to our claim that compliance was genuinely changed and that the treatment effect was mediated by reduction in voice power; CTCH had broad effects on outcomes, but the absence of (self-reported) change in voice activity argues against the notion that patients’ ratings were unreliable, and measures simply reflected the operation of a ‘halo’ effect in favour of CTCH across all measures.

Data obtained on prescription of neuroleptic and other drugs and provision of general mental health services during the course of the trial showed no difference between the groups and did not account for the effect of CTCH, but did underline their high level of service use linked to perceived risk. This suggests that the impact of CTCH we report here is unlikely to be accounted for by factors extraneous to the treatment. The pattern of neuroleptic use during the course of the trial showed no difference between the groups but did show a steady rise in neuroleptic prescription in the TAU group and a small reduction in the CTCH group. This suggests that concern about risk led to a raising of the dosage in those not receiving CTCH; this could reflect concern in clinicians as much as perceived benefit from CTCH.

The rise in neuroleptic use in TAU was correlated with reducing compliance; in CTCH the opposite was observed, i.e. reducing compliance was in line with reducing medication. There is a theoretical possibility that TAU participants were under-medicated and that the rise in medication prescription was responsible for the reduction in compliance (this could not account for the reduction in compliance in CTCH). This strikes us as unlikely for three reasons: first, both groups were receiving medication well in excess of British National Formulary (British Medical Association & Royal Pharmacuetical Society of Great Britain, 2003) and other guidelines, including widespread use of atypicals and clozapine; second, at no point did dosage correlate with compliance, power or PANSS scores; and finally, using drug dosage as covariate did not affect the results. If the TAU group were under-medicated, this would serve to under-estimate the effect size of CTCH, as compliance would be less likely to change over time. We believe that these differential changes in medication prescription reflect, as we indicate above, (understandable) clinician anxiety about this very high-risk group.

Nevertheless, it remains a possibility that non-specific aspects of the therapy were responsible for the effects. We believe, however, that the large correlation between changes in voice power and compliance by 6 months (0.63) strongly supports our contention that this aspect of the relationship with the voice (power) is the key independent variable. Whether it is cognitive therapy alone that brought about this change cannot be determined from these data, although we have clear evidence that the therapist adhered to protocol (see Method) and therefore we can be reasonably confident that the intervention itself was targeted at voice power and compliance.

The heterogeneity of the diagnosis of the sample is arguably a weakness. However, this was a pragmatic trial of the effect of CTCH on command hallucinations, and we decided to include all those who met the broad criteria for psychosis, irrespective of clinical diagnosis, to improve the generalisability of the findings. A second criticism is the apparently unequal numbers of those diagnosed with schizophrenia in each group (16 in TAU, 11 in CTCH; see Table 2). However, on the wider and widely used categorisation of schizophrenia and related disorders (ICD–10 F20–23, which includes schizoaffective disorders), this apparent difference becomes marginal in the other direction (16 in TAU, 15 in CTCH). Those with other diagnoses are also acceptably distributed, as are the scores on positive and negative symptoms. We would point out that the PANSS positive score was >20 in both groups (s.d. 3), indicating that our sample were indeed ‘psychotic’, notwithstanding the clinical diagnoses.

We feel the ‘real world’ relevance of the study is particularly strong. The sample as a whole was a severely distressed and a generally high-risk group. Approximately 55% of those eligible took part (i.e. 38 out of 69), and 27% withdrew from the CTCH group, which is average for CBT in this population (Reference Norman and TownsendNorman & Townsend, 1999; Reference Durham, Guthrie and MortonDurham et al, 2003). Given that this was a high-risk group, we looked at the reasons for patient withdrawal. We found, for example, that one person believed that the voice might harm or kill them for disclosing too much information; another feared that talking during therapy made the voices worse, and only continued on condition that it was the patient's decision how much to disclose about the voices.

The need for a further trial

The client group in this study – all experiencing command hallucinations and all having recently acted upon their commands – are typical of one of the highest-risk groups in psychiatry, who represent a major concern to their case managers, responsible medical officers and relatives, and particularly to themselves. This group is generally regarded as being resistant to treatment, whether with medication or cognitive–behavioural therapy (CBT) – ‘conventional’ CBT for psychosis is less effective with voices (Reference Birchwood, Spencer, Maj and SartoriusBirchwood & Spencer, 2002) – and clinicians acknowledge equipoise in their management, as witnessed by the high level of referral to the trial. Our study showed that many clients felt themselves caught helplessly in a vortex of voice power, but found that CTCH gave them an opportunity to exert control by distancing themselves from their assumptions about voice power. For example, one client commented that, ‘I know now that the voices can't hurt me – I feel that I am in control now. I still hear the voices but they are not as powerful.’ Another client directly attributed his improvement to using ‘all the techniques that she [S.B.] taught me; not only have the voices disappeared, but I am sleeping and eating properly now’. CTCH is therefore responding to a major gap in the treatment for people with ongoing, distressing voices, and deserves further evaluation.

This study was not definitive. It has suggested an effect size of major clinical significance, but because the sample size was small and the study was only conducted in one part of the country, there is a need to replicate it in a large-scale RCT incorporating different loci and different therapists, affording the opportunity to understand for whom CTCH is most effective and how durable any effects might be. The durability question is of particular importance. There is a strand of psychiatric opinion that treatments for schizophrenia are only effective as long as they are active (Reference McGlashanMcGlashan, 1988) and perhaps, therefore, a more theoretical and clinically relevant question might be ‘how much further intervention is required to maintain the effect of treatment?’

Finally, Turkington et al (Reference Turkington, Kingdon and Chadwick2003) observe in a recent editorial that current research into CBT for schizophrenia, although promising, is too imprecise, and that the way forward is to address specific questions, such as which are the active ingredients. They argue that trials with process measures ‘will allow further clarification of the crucial elements of CBT for psychosis’ (Reference Turkington, Kingdon and ChadwickTurkington et al, 2003: p. 98). Despite its limitations, we believe the present study is a step in this direction, in which the problem, the rationale, the intervention and the outcome are clearly specified and have a theoretical integrity and transparency, mediated through the process of the appraisal of voices’ power.

CLINICAL IMPLICATIONS

1. ▪ Cognitive therapy for command hallucinations (CTCH) has a comparatively large effect in reducing compliance with commands and delusional distress.

2. ▪ CTCH significantly reduces the impact of ‘power’ beliefs which, according to our theory, have a causal role in compliance and are therefore a risk factor.

3. ▪ CTCH is the first practical intervention that we know of that has a specific effect on compliance with command hallucinations.

LIMITATIONS

1. ▪ This pilot study needs to be replicated in a full-scale randomised controlled trial.

2. ▪ Although the treatment effect was mediated by a reduction in perceived voice power, we do not know if cognitive–behavioural therapy alone is responsible for this effect.

3. ▪ Although the study has measured effects at 6 months’ follow-up, this is a relatively short time frame and we have no measure of longer-term effects.