Adult attention-deficit/hyperactivity disorder: neuropsychological correlates and clinical presentation

Impaired spatial working memory in adults with attention-deficit/hyperactivity disorder: comparisons with performance in adults with borderline personality disorder and in control subjects

OBJECTIVE

This study investigated a previous claim that working memory may be 'particularly impaired' in adult attention-deficit/hyperactivity disorder (ADHD), compared with other psychiatric disorders which affect frontal lobe-mediated executive functions.

METHOD

Performance on spatial working memory (SWM) and two additional tasks were investigated for adult patients selected on the basis of DSM-IV ADHD (n = 19), adult patients selected on the basis of borderline personality disorder (BPD) (n = 19), and non-clinical control subjects (n = 19). Groups were matched for age, verbal IQ and gender.

RESULTS

Analysis of variance showed that the ADHD group had significant impairment of SWM performance relative to the non-clinical controls. Although there was a trend towards impairment in the BPD group relative to non-clinical controls, this did not reach significance.

CONCLUSION

The results are consistent with the claim that aspects of working memory are 'particularly impaired' in adult ADHD. Also, the BPD group had a longer deliberation time for one of the additional tasks, compared with the ADHD group, which indicated that the patient groups may have different patterns of neuropsychological impairments.

Targeting the dopamine D1 receptor in schizophrenia: insights for cognitive dysfunction

BACKGROUND AND RATIONALE

Reinstatement of the function of working memory, the cardinal cognitive process essential for human reasoning and judgment, is potentially the most intractable problem for the treatment of schizophrenia. Since deficits in working memory are associated with dopamine dysregulation and altered D(1) receptor signaling within prefrontal cortex, we present the case for targeting novel drug therapies towards enhancing prefrontal D(1) stimulation for the amelioration of the debilitating cognitive deficits in schizophrenia.

OBJECTIVES

This review examines the role of dopamine in regulating cellular and circuit function within prefrontal cortex in order to understand the significance of the dopamine dysregulation found in schizophrenia and related non-human primate models. By revealing the associations among prefrontal neuronal function, dopamine and D(1) signaling, and cognition, we seek to pinpoint the mechanisms by which dopamine modulates working memory processes and how these mechanisms may be exploited to improve cognitive function.

RESULTS AND CONCLUSIONS

Dopamine deficiency within dorsolateral prefrontal cortex leads to abnormal recruitment of this region by cognitive tasks. Both preclinical and clinical studies have demonstrated a direct relationship between prefrontal dopamine function and the integrity of working memory, suggesting that insufficient D(1) receptor signaling in this region results in cognitive deficits. Moreover, working memory deficits can be ameliorated by treatments that augment D(1) receptor stimulation, indicating that this target presents a unique opportunity for the restoration of cognitive function in schizophrenia.

Neuropsychological function in adults with attention-deficit/hyperactivity disorder

This article reviews the current state of the literature pertaining to the neuropsychological dysfunctions that are found in children and adults with attention-deficit/hyperactivity disorder (ADHD). Be-cause considerable controversy has existed about the nature and validity of adult ADHD, this article will aid clinicians in develop-ing a better understanding of the empirical literature on neuropsychological function in ADHD throughout the lifespan.

Modafinil improves cognition and response inhibition in adult attention-deficit/hyperactivity disorder

BACKGROUND

Modafinil, a novel cognitive enhancer, has a clinical profile similar to conventional stimulants such as methylphenidate, despite a seemingly different mechanism of action. Modafinil selectively improves neuropsychological task performance in healthy volunteers, possibly through improved inhibitory control. We examined whether modafinil induced similar improvements in adults with attention-deficit/hyperactivity disorder.

METHODS

Twenty patients with a DSM-IV diagnosis of attention-deficit/hyperactivity disorder were entered into a double-blind, randomized, placebo-controlled crossover study using a single 200 mg dose of modafinil.

RESULTS

Modafinil produced a similar pattern of cognitive enhancement to that observed in healthy adults, with improvements on tests of short-term memory span, visual memory, spatial planning, and stop-signal motor inhibition. On several measures, increased accuracy was accompanied by slowed response latency. This alteration in the speed-accuracy trade-off may indicate that modafinil increases the ability to "reflect" on problems coupled with decreased impulsive responding. Improvements were also seen in sustained attention, which was unaffected in healthy subjects.

CONCLUSIONS

If these benefits are shown to be maintained with chronic administration, modafinil may have potential as an important therapy for attention-deficit/hyperactivity disorder with a similar effect to stimulants such as methylphenidate in improving stop-signal response inhibition but without the side effects commonly experienced with amphetamine-like drugs.

Methylphenidate improves response inhibition in adults with attention-deficit/hyperactivity disorder

BACKGROUND

Response inhibition is an executive function that requires voluntary control over responses when there is a change of context. The right inferior frontal cortex is necessary for response inhibition, and a deficit in right frontostriatal circuitry might underlie attention-deficit/hyperactivity disorder (ADHD). Many studies of childhood ADHD have demonstrated impaired response inhibition and its amelioration by methylphenidate (MPH). The current study tested response inhibition and the effect of MPH in adult ADHD.

METHODS

Response inhibition was assessed with the "tracking" stop-signal test in 13 adults with a diagnosis of ADHD, both while taking and while not taking medication, and 13 healthy, unmedicated, age- and intelligence quotient-matched control subjects.

RESULTS

Stop-signal reaction time was significantly slower in unmedicated adults with ADHD relative to healthy control subjects, and this deficit was significantly ameliorated by medication.

CONCLUSIONS

Adult ADHD patients had a response inhibition profile similar to that produced by lesions to the right inferior frontal cortex, which was remedied by stimulant medication.

Differences in heterosocial behavior and outcomes of ADHD-symptomatic subtypes in a college sample

The purpose of this study was to explore heterosocial relational outcomes in a college-aged sample showing symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD). Using questionnaires and a behavioral observation task, dating, sexual, and social outcomes were examined in three groups: 24 non-ADHD controls, 27 ADHD-Combined (ADHD/C) Type, and 13 ADHD-Primarily Inattentive (ADHD/IA) Type. The ADHD/IA group showed a consistent pattern of passivity and inexperience and was perceived relatively negatively by female confederates, whereas the ADHD/C group reported increased sexual drive and early dating experience. The effects of externalizing comorbidity differed by DSM-IV ADHD subtype. These findings indicate that ADHD-symptomatic adults differ by DSM-IV subtype in the manifestation of heterosocial deficits. Results suggest specific and divergent types of psychosocial intervention with ADHD/C versus ADHD/IA clients.

Does maternal ADHD reduce the effectiveness of parent training for preschool children's ADHD?

OBJECTIVE

To assess the impact of maternal attention-deficit/hyperactivity disorder (ADHD) symptoms on the effectiveness of a parent training (PT) program for preschool ADHD.

METHOD

Eighty-three 3-year-old children with ADHD and their mothers selected from two community cohorts living in Hampshire, England (1992-93 and 1995-96, respectively), completed an 8-week PT program. ADHD symptoms and a number of other parent and child factors, including adult ADHD symptoms, were measured prior to the start of treatment (week 1: T1), immediately after treatment (week 8: T2), and at 15 weeks follow-up (week 23: T3).

RESULTS

Mothers were divided into three groups on the basis of their scores (T1) on the Adult AD/HD Rating Scale (high, medium, low). Children of mothers in the high-ADHD group displayed no improvement after PT, whereas the levels of ADHD symptoms of the children of mothers in either the medium or low ADHD groups reduced substantially (F(4,60) = 3.13, p < .05). This association persisted after other child and maternal factors were controlled for in multiple regression analyses (beta > .30, p < .05).

CONCLUSIONS

High levels of maternal ADHD symptoms limit the improvement shown by children with ADHD after a program of PT. This effect was unrelated to other aspects of maternal mental health and child functioning. The treatment of parental ADHD may be a prerequisite for the success of psychosocial interventions for childhood ADHD.