Neuropsychological impairments in crack cocaine-dependent inpatients: preliminary findings

Abstracts

OBJETIVO: Embora o uso de cocaína seja um problema significativo de saúde pública, há uma relativa escassez de dados científicos sobre as conseqüências neurocognitivas decorrentes da exposição à substância. MÉTODOS: Esse estudo avaliou a associação entre dependência de cocaína e crack e desempenho cognitivo. Uma ampla bateria de testes neuropsicológicos foi aplicada a 15 dependentes de cocaína, em abstinência por duas semanas, em tratamento em regime de internação, e em 15 sujeitos controles, não usuários de drogas, pareados por idade, sexo, escolaridade, nível sócio-econômico, lateralidade e QI. RESULTADOS: Os resultados preliminares mostraram significação estatística (p<0,05) em testes de atenção, fluência verbal, memória visual, memória verbal, capacidade de aprendizagem e funções executivas. CONCLUSÃO: Esses dados mostram evidências de que o abuso de cocaína está associado a déficits cognitivos, semelhantes aos que ocorrem em transtornos cognitivos, possivelmente relacionados a problemas em regiões cerebrais pré-frontais e temporais. O conhecimento dos danos neuropsicológicos específicos pode ser útil no planejamento de programas de prevenção e tratamento mais efetivo para abuso de cocaína/crack.

Cocaína crack; Abuso de substâncias; Cognição; Testes neuropsicológicos

BRIEF REPORT

Neuropsychological impairments in crack cocaine-dependent inpatients: preliminary findings^*

Paulo J Cunha^I; Sergio Nicastri^{I, II}; Luciana P Gomes^I; Renata M Moino^I; Marco A Peluso^I

^IGrupo Interdisciplinar de Estudos de Álcool e Drogas (GREA), Departamento e Instituto de Psiquiatria da Faculdade de Medicina da Universidade de São Paulo (USP)

^IIPrograma de Álcool e Drogas (PAD) do Hospital Israelita Albert Einstein (HIAE)

^{Correspondence}

ABSTRACT

OBJECTIVE: Although cocaine use is a significant public health problem, there is relative paucity of scientific data on long-term neurocognitive consequences of the exposure to the substance.

METHODS: This study examined the association between crack cocaine dependence and neuropsychological performance. An extended battery of neuropsychological tests was administered to 15 abstinent cocaine abusers, inpatients in abstinence for two weeks, and 15 non-drug-using control subjects matched for age, gender, education, socio-economic status, handedness and IQ.

RESULTS: The preliminary findings showed statistical significance (p<0,05) on differences of performance in attention, verbal fluency, verbal memory, visual memory, learning ability and executive functions.

CONCLUSIONS: These results represent evidences that cocaine abuse is associated with decrements in cognitive functioning, similar to cognitive disorders associated to prefrontal and temporal brain impairments. Knowledge of specific cognitive deficits in cocaine abusers may be useful for designing more effective substance abuse prevention and treatment programs.

Keywords: Crack cocaine. Substance-related disorders. Cognition. Neuropsychological tests.

Introduction

Cocaine/crack abuse is associated with several physical, psychiatric and social problems. It is estimated that 14 million people over the world have used cocaine in the last decade.¹ In Brazil, according to the First Home Survey on the use of Drugs, performed at the Brazilian Center of Information on Psychotropic Drugs (CEBRID), it was found that 7.2% of male subjects, aged 25 to 34 years, had already used the drug,² and recent epidemiological data show that cocaine/crack use has been rising among high school and elementary students,³ as well as among patients who seek for treatment in specialized clinics.⁴

Although certain neurological complications can occur in association with the use of cocaine/crack, it seems that there is no consensus among researchers regarding the cognitive impairment related to the use of the drug.^5,6 Therefore, a better knowledge about these issues will contribute for the development of preventive and treatment programs for cocaine/crack dependent subjects, as they involve cognitive-behavioral approaches.⁷

The objective of this study was to assess the neuropsychological performance of cocaine/crack-dependent subjects, during the second week of abstinence.

Sample and methods

This is a cross-sectional study, with 30 subjects, divided in two groups, one with cocaine/crack-dependent subjects (n=15) and the other, with normal volunteers (n=15), recruited in the community. Cocaine-dependent subjects were under specialized treatment programs (hospitalization), at the Interdisciplinary Group of Studies on Alcohol and Drugs (GREA), Institute of Psychiatry of the Medical School of the University of São Paulo and at the Therapeutic Community of the APOT (Campinas, SP, Brazil). Groups were matched by variables which could affect the results of the neuropsychological tests: age, gender, education, socioeconomic level and handedness. Exclusion criteria for the study were: significant problems at birth or in the psychomotor development, other DSM-IV axis I psychiatric diagnoses (APA, 1994); use of psychiatric medication; history of head trauma or neurological problems; medical problems which could affect the central nervous system; learning disorder.

Subjects were referred to an initial interview, in order to obtain the informed consent regarding the project and, afterwards, submitted to a neuropsychological battery, and for cocaine/crack-dependent subjects the evaluation was performed in the second week of drug abstinence.

The following areas of the cognitive functioning were assessed: attention (Trail Making Test - TMT, Stroop Color Word Test – SCWT and – Forward Digits FD and Backward Digits – BD, WMS-R),⁸ memory (Logical Memory – LM - I and II - WMS-R, Visual Reproduction – VR - I and II - WMS-R and Recall of the Rey-Osterrieth Complex Figure - ROCF),⁸ learning (Buschke Selective Reminding Test – BSRT),⁸ executive functions (Wisconsin Card Sorting Test – WCST⁸ and Frontal Assessment Battery – FAB⁹), visuospatial functions (Copy of the ROCF and Block Design – WAIS-R),⁸ language (Vocabulary – WAIS-R, Controlled Oral Word Association Test – COWAT – and Boston Naming Test – BNT)⁸ and intellectual functions (Vocabulary and Block Design, WAIS-R).⁸

Regarding the statistical analysis, comparisons between variables were performed with Student t tests for independent variables (continuous variables) or with Fisher exact test (categorical variables). Statistical significance level was a = 0.05 and all tests were two-tailed.

Results

There were no statistically significant differences between patients and controls regarding age, gender, education and socioeconomic level. Cocaine/crack-dependent subjects in average started using the drug at 18.41 years of age and the mean time of use was 10.3 years, and patients used the substance, in average, five days a week. Although all the subjects included in this study had a drinking history, most patients (66.6%) drank little or even had not ingested alcohol in the month prior to the hospitalization.

Regarding the results of the neuropsychological tests (Table 1), the performance of cocaine/crack-dependent subjects was significantly decreased in the FD and BD (WMS-R) tests, wich are measures of the attention ability.

Regarding the executive functions, patients had a poorer performance in the FAB and, in language functions, they produced less words started by letters F, A and S, in the COWAT.⁸

In the memory functions, there was difference in the capability of visual recovery, since patients had greater difficulty to recall figures after 30 minutes, both in the VR II (WMS-R) and in the ROCF.⁸

Regarding verbal memory and learning, cocaine/crack-dependent subjects had poorer scores than controls, with statistical significance (p<0.05) in the items Total Recall, Long-Term Retrieval (LTR), Long-Term Storage (LTS), Consistent Long-Term Retrieval (CLTR), Randomic Long-Term Retrieval (RLTR), Reminder and Recall after 15 minutes in BSRT.⁸

Estimated Intellectual Quotient (IQ) in cocaine/crack-dependent subjects was not statistically different from that found in the group of normal controls (p>0.05).

Discussion

In this study, the assessment of the attention ability showed performance differences between cocaine/crack-dependent subjects and normal controls, what has been frequently observed in other investigations.¹⁰ However, after a review on the subject, Horner⁵ claimed that there is still no consistency regarding the findings of attention deficits among cocaine/crack-dependent subjects, due mainly to the different methodologies applied and to the lack of more controlled studies. Further studies are necessary in order to verify the nature and severity of the attention deficits associated with cocaine, as they have a direct clinical implication in the treatment.^7,10 Alterations in the capability of retaining and manipulating information in the mind (attention and working memory), such as those found in the FD and BD (WMS-R) tests, are related to a poorer retention in the treatment.¹¹

We detected alterations in the performance of cocaine/crack-dependent patients in executive function tests, present in the FAB.⁹ Recent studies have observed pre-frontal alterations in cocaine/crack-dependent subjects, associated with their decision-making deficits¹² and with the neurobiological bases of substance dependences.¹³

The results of this study revealed statistically significant differences in the tests of phonological verbal fluency (letters F, A and S),⁸ showing significant deficits of verbal expression. Although these alterations have already been observed in previous studies,¹⁰ the issue is still unsolved in the literature, as some researches even found a better verbal fluency in subjects dependent on this drug.¹⁴ The hypothesis for that is the probable flaw of these studies regarding the inclusion of outpatients, who could be under the effect of the substance, considering that cocaine/crack intoxication could stimulate the verbal production of these patients.

We also found delayed visual memory deficits (after 30 minutes) in cocaine/crack-dependent patients, both in VR II (WMS-R) and in the ROCF Recall.⁸ Besides, BSRT⁸ showed consistent failures in the memory recovery and verbal learning of dependent subjects, suggesting that these patients have problems in the storage of new verbal information, possibly associated with functional alterations of the frontal and temporal lobes.⁸ Studies have demonstrated that cocaine acts and promotes alterations in hyppocampal regions, modifying the Long-Term Potentiation (LTP) mechanism, involved in the process of formation of new memories.¹⁵ The decrease in the availability of dopamine and serotonin in these areas during abstinence has been associated with learning and memory deficits. Similar results regarding memory and learning deficits have already been described in the international literature,¹⁰ and they can impair significantly the patient’s ability to incorporate strategies for relapse prevention.^7,10

This study was able to detect neuropsychological deficits described in the literature, such as in the attention, language, memory, learning, and executive functions. Despite our cautious delineation of the inclusion and exclusion criteria of participants, the use of a matched control group and the control of abstinence (hospitalization regime), there are limitations in this study. First, the still relatively small size of the sample. Second, the need of a stricter control regarding the existence of neuropsychiatric symptoms which could influence the results. For example, it is believed that the analysis of a previous diagnosis of attention deficit hyperactivity disorder (ADHD), on each of the participants, could provide more evidence regarding the causality of the found alterations. Other information that should be better investigated is the presence and severity of the depressive and anxious symptoms in the subjects. Besides, the cross-sectional delineation of the study prevents the prospective visualization of the found cognitive deficits and to know whether they persist or not during the abstinence.

These data highlight the importance of performing more studies in this area, involving larger samples, a stricter control of the variables which may influence the results, and monitored follow-up of subjects.

Conclusions

The preliminary results of this investigation showed neurocognitive impairment in cocaine/crack-dependent subjects, when compared to normal subjects. We found alterations in attention, verbal fluency, visual memory, verbal memory, learning ability and executive functions. These data show evidence that cocaine abuse is associated with significant neuropsychological deficits, similar to those that occur in cognitive disorders, possibly related to problems in the prefrontal and temporal brain regions. The knowledge of specific neuropsychological impaiments can be useful in the planning of more effective preventive and treatment programs for cocaine/crack abuse.

Acknowledgements

References

Sponsor: Fundação de Amparo a Pesquisa do Estado de São Paulo - FAPESP. Auxílio Pesquisa: Processo nº 00/12081-5.

Received 10.02.2003

Accepted 04.11.2003

Pesquisa realizada no Grupo Interdisciplinar de Estudos de Álcool e Drogas (GREA), Departamento e Instituto de Psiquiatria da Faculdade de Medicina da Universidade de São Paulo (USP) e na Comunidade Terapêutica da Associação Promocional Oração e Trabalho – APOT (Campinas-SP).

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*

Dados desta pesquisa ("Neuropsychological impairment of cocaine dependent patients" e "Cocaine dependence impaired performance in a new neuropsychological battery sensitive to prefrontal functions –FAB") foram apresentados no Sixty-Sixth Annual Scientific Meeting do College on Problems of Drug Dependence (CPDD) e NIDA International Fórum, realizados de 11 a 17 de Junho de 2004, em San Juan, Puerto Rico (USA).

Publication Dates

• Publication in this collection
  27 Oct 2004
• Date of issue
  June 2004

History

• Received
  10 Feb 2003
• Accepted
  04 Nov 2003