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Rev. CEFAC vol.14 no.3 São Paulo May/June 2012 Epub Aug 26, 2011
Luciana Lopes Silva CostaI; Ana Luiza Gomes Pinto NavasII; Christian Cesar Cândido OliveiraIII; Lilian Ribeiro Caldas RattoIV; Kamila Helena Prior de CarvalhoV; Helio Rodrigues da SilvaVI; Cristiane LopesVII; Carla Andréa TieppoVIII
IGraduate Student, Department of Speech Pathology, School of Medical Sciences of Santa Casa of São Paulo, Brazil
IIPhD, Adjunct Professor, Department of Speech Pathology, School of Medical Sciences of Santa Casa of São Paulo, President Director of ABCD Institute, Brazil
IIIPhD, Department of Speech Pathology of School of Medicine, University of São Paulo, Brazil
IVPsychiatrist; Attending Physician of Irmandade da Santa Casa de Misericordia de São Paulo; Member of the Medical Staff of the Center for Integrated Mental Health Care of Santa Casa of Mercy of São Paulo, Brazil
VPsychiatrist;Specialist in chemical addiction program at Counseling and Treatment of Addiction PROAD Federal University of São Paulo UNIFESP; Member of the medical staff of the Center for Integrated Health Care Mental of Santa Casa of Mercy of São Paulo, Brazil
VIGraduate student in Health Sciences; Specialist in Clinical Analysis; School of Medical Sciences of Santa Casa de São Paulo, Brazil
VIIPhD, Molecular Scientist; Assistant Professor Department of Physiological Sciences, School of Medical Sciences of Santa Casa of São Paulo, Brazil
VIIIPhD Neuroscientist; Adjunct Professor Department of Physiological Sciences, School of Medical Sciences of Santa Casa of São Paulo; Teaching Assistant Department of Developmental Psychology, Catholic University of São Paulo, Brazil
PURPOSE: to evaluate the phonological working memory abilities and check possible influences of impulsivity in patients just included in treatment at the program for Alcohol and Drug users at the Center for Integrated Mental Health Care of Irmandade da Santa Casa de Misericordia de São Paulo (ISCMSP CAISM-SP, Portuguese initials).
METHOD: 29 patients: 21 males and 8 females, drug users, 37,9 ± 10.5 years old, 10.59 ± 3.53 years of schooling; And 30 volunteers: 19 males and 11 female, 32,4 ± 11,9 years old and 11.07 ± 3.29 years of schooling, without psychiatric history or substance abuse participated freely. The individuals were asked to attend the specific evaluation, aiming to assess: 1) phonological working memory for words and pseudowords, 2) impulsivity in its second order factors (attentional impulsiveness, motor and non-planning).
RESULTS: performance in the evaluation of phonological working memory of the individuals of drug users group compared to the control group showed a reduction in both, auditory word and pseudowords span , as well as the total number of correct words and pseudowords recall. In the evaluation of impulsivity, the group of drug users showed higher scores comparing to control individuals in all subtypes of impulsivity, including the total score of impulsivity. There were no correlations between impulsivity scores and word and/or pseudowords span.
CONCLUSION: this pattern of responses indicates impairment in verbal working memory processing and high level of impulsivity in this population of chronic drug users. The poor performance of chronic drug users on tests of phonological working memory is probably not due to increased impulsivity observed. The present results could helptreatment strategies planning focused on the detected changes.
Keywords: Memory, Short-Term; Impulsive Behavior; Substance-Related Disorders; Street Drugs
The consumption of psychoactive substances has always existed in human history since its inception, varying in amount, type and manner of drug use1. If there is a supremacy on one or another type of drug at one time, this is due to specific factors and characteristics of the historical moment in which we live2.
Psychoactive substances have different aims and very different pharmacological effects, although they all have the potential to cause addiction. The addiction of these substances or simply addiction can be defined as the loss of control over drug use or the compulsive seeking and use despite adverse consequences3.
The essential feature of substance addiction, according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)4 and International Classification of Diseases5, is the presence of a cluster of symptoms of cognitive, behavioral and physiological processes indicating that the individual continues to use a substance despite significant problems related to it.
The substance abuse is associated with neuropsychological deficits related to emotion, memory and executive functions6. The impairment in cognitive performance of drug users not only interferes with the general aspects such as quality of life, but also the inefficiency of these cognitive functions is directly related to the central aspect of addiction: the behavior and tendency to use drugs despite negative consequences7.
In a longitudinal study characterizing cognitive change, the authors found poor performance in verbal learning, verbal working memory and attention skills involved in adolescent drug users8. Improvements in development were observed in learning a word list after two weeks of abstinence and verbal working memory, after three weeks. While the attention deficits persisted even during the withdrawal period of three weeks8.
Working memory is the memory responsible for the temporary storage of information to perform a series of cognitive tasks9. The ability to maintain relevant information to the active processing is considered a crucial aspect of cognitive function. Working memory can be understood as a system of maintenance and temporary storage of information required to perform complex cognitive tasks involving reading, comprehension and reasoning10.
The verbal working memory system is particularly important given its role in linguistic processes involved in cognitive mechanisms. According to the literature, span tasks were designed to measure if the capacity of this memory is highly predictive of the performance in high-level cognitive activities such as understanding, reasoning and problem solving11.
The difficulty in working memory span is explained by the fact that the information to be retained is susceptible to decline over time. Thus, the performance of the individual on recall depends on the duration of the procedure, which then determines the retention period of the stimulus in memory. The longer the duration of the retention, the greater the span11.
Some authors12,13 investigated the possibility of storage in working memory capacity observing that maintenance and durability is fragile and limited. Phonological memory is influenced by the extent and frequency of verbal material and starts its development from the age of six. In order to assess the phonological component of working memory tasks it is widely used a task of digits and non-words or pseudowords repetition. The repetition of pseudowords assesses more accurately the phonological component since it is not influenced by semantics or syntax.
The executive processing is related to the human ability to obtain information by different brain systems, verbal or nonverbal, and act to produce new responses14. Working memory and inhibitory control are two cognitive processes that underlie the executive function. The first, refers to the ability to maintain and manipulate information in short-term to generate an action in the near future; and the latter, refers to a process that aims to suppress internal or external influences that might interfere with ongoing behavioral sequence14.
Losses in the executive control system of working memory may explain some of the cognitive and behavioral problems displayed by individuals who use multiple drugs, identified as more impulsive than the control group15.
Impulsive behavior can be defined from various viewpoints, including biological phenomenon, sociological and psychological16. Studies suggest a correlation between three factors: general verbal learning, impulsivity and attentional executive processing, emphasizing the importance of mnemonic aspects of impulsive behavior16.
Impulsive disorders are also characterized by a working memory decrease and impulsive personality correlates with low cognitive performance17. Impulsivity can also be defined as behavior characterized by a high level of anticipatory responses, held in a faster reaction time, compared to situations that require a decision18. Studies show impulsivity as the main feature for understanding vulnerability to impulse control disorders, such as drug addiction and associated with a higher sensitivity to the effects of dopaminergic drugs19.
The association between impulsiveness and the use and/or substance abuse has been investigated in animal models and in humans. In animal models of impulsivity, it was shown that mice with high levels of anticipatory responses on tasks of sustained visual attention (5-CSRT Five-choice serial reaction time) showed an increase in self-administration of cocaine20. In humans, this association has been demonstrated in studies with individuals addicted on alcohol, tobacco, marijuana and heroin, whose impulsive behavior scale measured by BIS-11 was higher than the control group21.
Chronic drug use produces deficits in general neuropsychological mechanisms, however, it is difficult to differentiate what effects are caused by each substance in users of polydrugs. The specific effects of a substance (eg. stimulant) and those produced by other substances (eg. depressor) may be superimposed even though the pharmacological effects are different7.
The aims of this study were to characterize and correlate the expression of phonological working memory and impulsivity in a group of drug users who seek care in a psychiatric clinic.
This was a quantitative, prospective and transversal study. We included 29 drug users for over 1 year, with no hearing problems, which spontaneously sought outpatient care in the Integrated Care Center of Mental Health of Santa Casa of Mercy of São Paulo (drug user group) and 30 individuals who had no history of drug use and no hearing problems (control group). The control group was selected among the students, trainees and employees of the School of Medical Sciences of Santa Casa of São Paulo.
The drug user group was characterized by: age 37.9 ± 10.5 years old; 10.59 ± 3.53 years of schooling: 7 with higher education, 8 had incomplete college, 8 with complete medium education, 2 with primary complete education and 4 with incomplete primary education. The demographic profile of the samples is shown in table 1. The profile of psychoactive substance use is: 6 individuals had used only alcohol, 7 had used two psychoactive substances, 5 had used three substances and 11 had used more than three substances concomitantly. Regarding the type of substance used: 26 individuals were alcohol users, 20 cocaine users, 19 marijuana users, 10 crack users, 3 lysergic acid users and 2 amphetamine users, as shown in Figure 1.
The exclusion criteria were individuals: 1) under 18 years old: 2) under imminent risk of violent behavior or violent tendencies detected by the psychiatrist, 3) with a history of hearing disorders, visual and/or fluency of speech, 4) with personality disorders detected by the psychiatrist. The individuals included were submitted to the specific tests described below, and then the data categorized according to type of addiction, age and education.
Each individual was assessed individually in two phases for a total of one hour duration. First, we assessed phonological working memory and then we completed the questionnaire on impulsivity.
Phonological working memory assessment
For the assessment of phonological working memory, tests were used to evaluate verbal memory capacity. More specifically, tests evaluated auditory sequential memory of words and pseudowords22.23. The memory test contains a sequence of 60 words and 42 pseudowords, which are the auditory stimuli. They are read to the research individual separately. All stimuli are disyllabic with the accent on the first syllable, and with a consonant-vowel-consonant-vowel (CVCV) pattern. These are considered the most frequent structure in Brazilian Portuguese. Five lists were presented with three blocks of stimuli with two, three, four, five and six sequences of words and four lists with three blocks of stimuli with two, three, four and five sequences of pseudowords.
The inter stimuli interval was one second for the two lists. The presentation took place by means of a recording software with speakers attached to a computer and the answers recorded on digital recorder. The volunteer was requested to hear the sequence of stimuli of a block and the end to repeat them in the correct order.
Barratt Impulsiveness Scale was used to assess impulsivity24. The version 11 was validated for use in Brazilian adults25. The BIS-11 is one of the most widely used instruments to measure impulsivity, with translation and validation for different languages. It consists of an instrument of 30 self-report items designed to assess personality and behavioral construction of impulsivity26,27. Generated total score of impulsivity ranging from 30 to 120, plus three other sub-scores: attentional, motor and not planning. Depending to the concept of components that range attentional impulsiveness is to make decisions faster. Cognitive, motor impulsivity involves acting without thinking, and impulsivity is not a lack of planning "vision of the future "or planning25.
This research was approved by the Ethics Committee of Irmandade da Santa Casa de Misericordia de São Paulo (ISCMSP), protocol number 143/08 and the individuals involved signed an informed consent form.
For auditory memory analysis we used Student t test and for the impulsivity analysis, we used the nonparametric Mann-Whitney test. Correlation analysis was performed between the results obtained in phonological working memory task with the scores presented in the impulsivity questionnaire. Correlation was evaluated by linear regression test, placing one of correlation factors to be tested on the abscissa and the other on the ordinate. The slope of the line was taken as the correlation factor.
We considered statistically significant result when p<0.05, for all comparisons performed .
After the evaluation of phonological working memory and impulsivity in chronic users of psychoactive substances (drug user group), legal or illegal, who sought outpatient treatment spontaneously in CAISM, some important deficits were detected when compared with control individuals (control group not drug users) and are described below.
In the assessment of phonological working memory it was evaluated four parameters: word span, pseudowords span, total recall of words and total recall of pseudowords. Compared with the control group, drug users had lower efficiency on auditory word span (3.8 ± 0.75 vs 3.3 ± 0.93 respectively, p = 0.0069*) and pseudowords (2.7 ± 2.2 vs 0.43 ± 0.78 respectively, p = 0.0024*). This reduction in efficiency of phonological working memory was also detected when comparing the total number of hits in the recall of words (41.6 ± 6.5 vs 34.3 ± 12.4, p = 0.0168*) and pseudowords (21.8 ± 4.8 vs 16.5 ± 6,9,08, p = 0.0071*), control groups and drug users, respectively. These data are presented in Figure 2. These results indicate that drug users are less efficient on the expression of phonological working memory.
In impulsivity, measured by the Barratt Impulsiveness Scale, the group of drug users had high scores in contrast to control individuals in all subtypes of impulsivity: no planning, motor and attention; including the total score of impulsivity, according to data presented in Figure 3. These results indicate that chronic users of psychoactive substances are more impulsive than controls.
After the analysis of phonological working memory and impulsivity of drug users and controls, we raised the possibility of a correlation between performance on tests of phonological working memory and impulsivity in the group of users. No correlation was found between these two parameters, as shown in Table 2. These results indicate that the decreased efficiency of phonological working memory is not due to greater impulsivity showed by drug users.
Assistance to users of alcohol and other drugs is under public health policy discussion, given the impact that this issue brings to the national public health in all countries. According to the Report on World Health28 (2001), from the 20 diseases in the age group between 15 and 44 years old for males, disorders due to alcohol intake are in second place, with 10%, and disorders due to the use of illicit drugs are in ninth position, with 3%. According to the report of the United Nations Office on Drugs and Crime 29 (UNODC) released in 2010, it is estimated that the number of drug users is around 155 and 250 million (or 3.5 to 5.7% of world population between 15 and 64) with 2.9% to 4.3% of marijuana users, 0.6% using derivatives of amphetamines and 0.4% of cocaine users. From the total, 40 million were identified as regular users.
The psychoactive substances regular use is associated with neuropsychological deficits related to emotion, memory and executive functions30. The impairment in cognitive performance of drug users not only interferes with the general aspects such as quality of life, working conditions and student life, but is also directly related to the central aspect of addiction: the behavior and tendency to use drugs despite the negative consequences7. Several experimental models have been applied to better understand the phenomenon of compulsive drug use. This behavior can be described as a condition associated with dysfunction of brain mechanisms responsible for decision-making capacity31.
The polydrug use is another hallmark of the current pattern of compulsive use, gradually replaced by exclusive use. This study characterized as all-inclusive, as it considered the inclusion of patients with chronic use of psychoactive substances varied licit, illicit and therapeutic drugs7,32 corroborating several studies that emphasize the difficulty with this population that makes use of many different substances in a short period of time, and often simultaneously.
In this study, the individuals from the group of drug users presented a significant reduction in the capacity of phonological working memory performance compared to ones of the control group, either on tests of auditory sequential memory for words or pseudowords. From these results, we concluded that there is an impairment in working memory ability in drug users of this study.
It was also observed the increase in scores of impulsivity in drug users. The results support studies showing that drug users have lower scores than controls in tasks involving attention, verbal learning and memory33,34, cognitive flexibility, impulse control35,36and selective processing 37. Studies also point to the fact that adult chronic users of drugs have impaired performance in tasks involving selective attention, suggesting a slowdown in information processing and difficulty in maintaining attention to relevant stimuli34.
The performance on tasks requiring this kind of memory is directly related to aspects of attention, motivation and cognition. It is described in the literature that drug users have increased levels of impulsivity38,39.
Studies with a population that use psychoactive substances chronically, such as tobacco, marijuana, cocaine and alcohol, showed impairments in cognitive functions involving self-control, and point to the fact that chronic drug users compared with nonusers, have decreased ability to inhibit responses, they were worse in the performance of tasks involving mental flexibility, control of visual attention and decision making40.
In this sense, it was found in the sample of individuals studied, which are drug users, increased impulsivity scores according to the BIS-11 in all sub-items: attentional, motor and non-planning impulsiveness.
To analyze the impact of increased impulsivity in the drug user group on words and pseudowords span, linear regression analysis was calculated, with the results obtained in phonological working memory and impulsivity sub-scores (Table 2). The lack of correlation found could mean that the working memory deficit observed is not directly related to impulsive behavior.
The fact that the individual drug users have high levels of impulsivity, does not mean that they necessarily must have a reduced ability to repeat words and pseudowords in the applied assessment of phonological working memory. However, the results show that besides the increased impulsivity, the sample population involved in this work also has important deficits in phonological working memory.
Considering the enormous impact that drug addiction causes to society, with a deep burden in education, health, economics, among others areas, it is absolutely pertinent investment in intellectual and economic efforts in order to characterize the drug user, to describe difficulties and cognitive inefficiency, and to find solutions to intervene in the process efficiently and positively, in order to help in rehabilitation.
The pattern of responses found in this study indicates involvement in the processing of phonological working memory and high level of impulsivity in a population of chronic users of psychoactive substances compared with controls not drug users.
The poor performance of drug users in the trials involving phonological working memory was not due to increased impulsivity observed.
More studies are needed to verify the nature and severity of phonological working memory deficits associated with the use of psychoactive substances, and its direct implication in clinical treatment. These analyses could help to suggest treatment strategies directed at the detected deficits.
To Irmandade da Santa Casa de Misericórdia de São Paulo and Fundação Arnaldo Vieira de Carvalho for their support in developing this study.
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Mailing Address: Received in: 11/21/2010 Conflict of interest: non-existent
Luciana Lopes Silva Costa
Rua Dr. Cesário Motta Jr., 61
São Paulo SP Brazil
Accepted in: 02/15/2011
Received in: 11/21/2010
Conflict of interest: non-existent