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在一项记忆力缺失／过动异常（ADHD）成人的功能性脑部断层扫描（fMRI）研究中，相较于控制组，男性脑部的四个区域在进行记忆工作时的神经活性较低，但女性并没有这样的现象；这些发现发表于美国儿童与青少年精神医学第54届年会座谈会上。
来自麻州波士顿哈佛医学院的发表者Eve M. Valera博士向Medscape精神医学表示，我并不预期看到女性ADHD病患与控制之间没有差异；这给临床医师的讯息是，许多ADHD研究是针对男性，且我们对于男性的认知并不一定适用于女性身上。
【文献中男性病患占大多数】
Valera博士表示，大约5%的成人罹患ADHD，且这与许多功能受损有关，例如增加忧郁、药物滥用、以及工作上的障碍等等。
她附带表示，在文献中，有关于男性的资讯占绝大多数，她在一项非全面性的文献搜寻中发现，在fMRI的研究中，其中15个研究的受试者全部都是男性、6个研究的受试者以男性为主、仅有2个研究全部收纳女性受试者。
她指出，虽然在儿童流行病学样本中，因ADHD转介求诊的男、女性比例为3比1，但在成人身上会达到比较平衡的比例，男性比上女性为1.5比1；她附带表示，男性更容易表现出行为异常，但女性比较可能有ADHD注意力不集中的症状。
最近的MRI研究显示，相较于控制组，成人ADHD病患在进行口语记忆工作时，脑部枕叶与小脑区域的活化较差；然而，这样的结果是否可以应用于男性与女性身上则是未知的。
研究者在目前这项研究里假设相较于控制组，男性与女性在脑部额叶及前额叶皮质的活性较低，但是女性的差异可能较不明显。
研究样本包括44个罹患ADHD个体（21位女性、23位男性）与49个控制组个体（26位女性、23位男性），这些受试者的年龄约莫30多岁，且教育程度高。
为了要探测神经功能，这些受试者在进行一项双回溯口语记忆工作时接受fMRI检验，在这项工作中，受试者会看到一系列字母在荧幕上闪过，且他们被教导在最近闪过去的两个字母是一样的时候，按下"是"的按钮，但在其他的情况下则是按下"否"的按钮；举例来说，看到X、C、M与C这些字母的时候，答案应该是"否"、"否"、"否"与"是"。
【男性与女性ADHD病患之间的差异】
在记忆工作测试中，男性与女性的行为是差不多的，但是男性的神经活化在脑部的4个区域与控制组有差异，至于女性则没有这样的现象；相较于控制组受试者，男性ADHD病患脑部的右额叶、左顶叶、左小脑枕叶、与双侧亚皮质区域的神经活性较低，这些区域与工作记忆有关；令人惊讶的，罹患ADHD女性并没有任何脑部区域显示显著的神经活性下降。
Valera博士表示，这些初期研究结果突显了对临床医师与其他人而言，当评估ADHD研究结果时，要注意到潜在的性别差异，她补充需要之后的研究，以更多的女性人数来证实这些结果。
Valera博士表示接受美国Shire公司的报酬。
Sex Differences in Brain Activity Seen During Memory Task in Adult ADHD
By Marlene Busko
Medscape Medical News
In a functional magnetic resonance imaging (fMRI) study of adults with attention-deficit/hyperactivity disorder (ADHD) compared with controls, men but not women had decreased neural activity in 4 brain areas while performing a working memory task.
These findings were presented in a symposium at the American Academy of Child & Adolescent Psychiatry 54th Annual Meeting.
"I did not expect to see no differences between women with ADHD and healthy controls," presenter Eve M. Valera, PhD, from Harvard Medical School, in Boston, Massachusetts, told Medscape Psychiatry. The take-home message for clinicians is that "a lot of research is focused on males . . . and what we know about males may not necessarily apply to females."
"Males Dominate the Literature"
About 5% of adults have ADHD, which is associated with impairments such as increased depression, substance abuse, and employment difficulties, Dr. Valera said.
"Males dominate the literature," she added, noting that in a noncomprehensive literature search of fMRI studies of ADHD, she found 15 studies with all-male subjects, 6 with mostly male subjects, and only 2 with all-female subjects.
Although referrals for ADHD in childhood epidemiologic samples are 3 to 1 for boys vs girls, by adulthood this shifts to a more equal proportion of 1.5 to 1 for men vs women, she said. Males are more likely to exhibit behavior disorders, whereas women are more likely to have the inattentive subtype of ADHD, she added.
Recent fMRI studies showed that relative to controls, adults with ADHD had decreased activation in occipital and cerebellar regions while performing a verbal working memory task. It was unknown, however, whether these results would apply equally to men and women.
The researchers in the current study hypothesized that relative to controls, males and females would show hypoactivity in the frontal and prefrontal cortex, but females would show subtler differences.
The sample comprised 44 individuals with ADHD (21 women, 23 men) and 49 controls (26 women, 23 men) who were in their 30s and had a fairly high intelligence level.
To probe neural functioning, the subjects underwent fMRI while they performed a 2-back verbal working memory task. In this task, participants were shown a series of letters flashing on a screen and were instructed to press the "yes" button every time they saw the same letter as 2 letters back and to press the "no" button in other cases. For example, the correct response to seeing the letters X, C, M, and C is "no," "no," "no," and "yes."
Differences Between Men and Women With ADHD
Both men and women behaved similarly during the working memory test, but neural activation in men, but not in women, differed from the controls in 4 areas of the brain. Relative to control subjects, men with ADHD had significant clusters of reduced neural activation in the right frontal, left parietal, left cerebellar occipital, and the bilateral subcortical regions of the brain — areas that are associated with working memory. Surprisingly, women with ADHD did not have any brain areas with significantly reduced neural activation.
These preliminary findings highlight that it is important for clinicians and others to be aware of potential sex differences when evaluating ADHD research results, said Dr. Valera, adding that further studies are needed that include sufficient numbers of women.
Dr. Valera reports receiving honoraria from Shire US Inc.
American Academy of Child & Adolescent Psychiatry 54th Annual Meeting: Symposium 2. October 23-28, 2007.