Evidence of persistent executive function deficits in cannabis dependence after one month of abstinence

Evidências de déficits executivos persistentes após um mês de abstinência na dependência de maconha

LETTERS TO THE EDITORS

Evidence of persistent executive function deficits in cannabis dependence after one month of abstinence

Evidências de déficits executivos persistentes após um mês de abstinência na dependência de maconha

Dear Editor,

Marijuana is the most commonly used illicit drug around the world. Information about risks is important for prevention and treatment strategies. In this regard, a relevant and well conducted review article was published in the Revista Brasileira de Psiquiatria by Almeida et al., which has concluded that chronic cannabis users (CCU) present executive cognitive functions (ECF) deficits. The authors reviewed nine studies of CCU that showed impaired abstract reasoning, concept formation, and mental flexibility.¹ ECF may represent a very relevant target for rehabilitation strategies, since ECF deficits are associated with poorer outcomes in treatment.² In addition, the literature discussing whether ECF-related deficits persist after a period of abstinence is contradictory.³ Pope et al. did not find evidences to support that CCU who were 28-day abstinent have persistent ECF-related deficits.⁴ However, Bolla et al. suggested that heavy CCU had persistent dose-related cognitive and ECF-related deficits on a range of neuropsychological tests, even after 28 days of abstinence.⁵ The aim of this letter is to report a case study that met the diagnostic criteria for cannabis dependence and was followed for a period of 30 days in an inpatient unit. After signing the informed consent, the patient was submitted to a very careful neuropsychological assessment (NA) focused on ECF, at the treatment entry (1^st NA) and after 30 days (2^nd NA).

Case report: A 36 year-old man was admitted to the impulsive behavior ward of the Institute of Psychiatry (IPq), Clinicas Hospital, Medical School, Universidade de São Paulo (FMUSP). He was 13 years old when he began to smoke cannabis and he was 16 when he started to use it almost weekly (every weekend). His cannabis use increased progressively and at 20 years old he started to smoke daily (one week was the maximum withdrawal period) until he was admitted to the ward unit. He has been using three joints a day during the last eight months. The NA was based mainly on ECF-related tests. The results in the 1^st NA showed good estimated intellectual efficiency (Intellectual Quotient, IQ: 105, average), semantic knowledge (vocabulary, from the Wechsler Adult Intelligence Scale, Third Edition, WAIS-III) and verbal fluency (Controlled Oral Word Association Test, COWAT - see Table 1), although the tests demonstrated neuropsychological impairments in processing speed/basic attentional processes (Trail Making Test, TMT - part A, Stroop Color Word Test, SCWT - parts I and II), working memory (Backward Digits, BD), planning (The Rey-Osterrieth Complex Figure Test, ROCFT), decision making (Iowa Gambling Test, IGT), abstraction (Frontal Assessment Battery, FAB, subtest),⁶ autonomy (FAB subtest) and inhibitory control (FAB subtest) corresponding to deficits associated with CCU in the literature.^4,5 After one month of abstinence (2^nd NA), which was verified by self-report and supervised by the clinical staff, there was an improvement in decision-making, planning, verbal fluency, abstraction and autonomy, as well as a slight improvement in working memory and mental flexibility (perseverative errors – Wisconsin Card Sorting Test, WCST). In spite of this, his performance on ECF tasks such as TMT - Part B and BD remained somewhat below the normal range (Low Average). Additionally, the patient remained with an important deficit in the FAB's inhibitory control subtest (Figure 1) and he had a poorer performance in attention span (Forward Digits, FD) and failures to maintain set in WCST. In his daily life he had problems associated with finances, job, and family (the patient was unable to financially support himself and to have a satisfactory relationship with his parents, especially with his mother).

It is relevant to highlight that in the 1^st and 2^nd NA, the patient has showed apparently unexpected superior results in WCST (especially in completed categories). Yet, WCST impairment findings in CCU are rather inconsistent.^4,5 Also, his abstraction performance in WCST corresponds to his good estimated premorbid intellectual efficiency (showed by Vocabulary – WAIS-III). On the other side, his poor performance on the TMT and on the SCWT (part I and II) could have occurred due to processing speed deficits. It is possible that the patient revealed different performances on diverse tests (WCST, TMT and SCWT), because they measure distinct functions.

Despite some improvement in ECF, the patient did not reach a normal functioning in the 2^nd NA. Also, the FAB detected inhibitory control impairments that persisted throughout the period of one month of abstinence. Considering that there were no differences regarding the severity of depressive and anxious symptoms between the 1^st and 2^nd NA, the persistent ECF-related deficits were unlikely to be associated with withdrawal effects.

In conclusion, even after 30 days of withdrawal, ECF-related deficits were observed in cannabis dependence that may be associated with problems in the patient's daily life. The improvement seen in certain cognitive functions should be carefully interpreted. First, where there were indeed improvements, they were modest, and impaired performance appeared to persist across many measures. Second, certain neuropsychological tasks such as ROCFT are subject to practice effects due to repetitive testing. Longitudinal studies are needed for further investigation on the persistence of ECF changes and the impact on the daily activities of cannabis users.

Priscila Dib Gonçalves, André Malbergier,

Arthur Guerra de Andrade

Interdisciplinary Group of Studies on Alcohol and Drugs

(GREA), Department of Psychiatry (IPq), Medical School,

Universidade de São Paulo (USP), São Paulo SP, Brazil

Maria Alice Fontes

Interdisciplinary Laboratory of Clinical Neurosciences

(LiNC), Department of Psychiatry, Universidade Federal de São

Paulo (UNIFESP), São Paulo, SP, Brazil

Paulo Jannuzzi Cunha

Interdisciplinary Group of Studies on Alcohol and Drugs

(GREA), Department of Psychiatry (IPq), Medical School,

Universidade de São Paulo (USP), São Paulo SP, Brazil

Equilibrium Program, Institute of Psychiatry (IPq),

Universidade de São Paulo (USP), São Paulo SP, Brazil

• 1. Almeida PP, Novaes MA, Bressan RA, Lacerda AL. Review: executive functioning and cannabis use. Rev Bras Psiquiatr 2008;30(1):69-76.
• 2. Aharonovich E, Brooks AC, Nunes EV, Hasin DS. Cognitive deficits in marijuana users: effects on motivational enhancement therapy plus cognitive behavioral therapy treatment outcome. Drug Alcohol Depend. 2008;95(3):279-83.
• 3. Solowij N, Pesa N. Cognitive abnormalities and cannabis use. Rev Bras Psiquiatr 2010;32(Suppl 1):S31-40.
• 4. Pope HG, Gruber AJ, Hudson JI, Huestis MA, Yurgelun-Todd D. Neuropsychological performance in long-term cannabis users. Arch Gen Psychiatry 2001;58(10):909-15.
• 5. Bolla KI, Brown K, Eldreth D, Tate K, Cadet JL. Dose-related neurocognitive effects of marijuana use. Neurology. 2002;59(9):1337-43.
• 6. Cunha PJ, Nicastri S, Andrade AG, Bolla KI. The Frontal Assessment Battery (FAB) reveals neurocognitive dysfunction in substance-dependent individuals in distinct executive domains: abstract reasoning, motor programming, and cognitive flexibility. Addict Behav 2010;35(10):875-81.

Publication Dates

• Publication in this collection
  07 Feb 2011
• Date of issue
  Dec 2010