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ADHD is a difficult diagnosis to make, although there are several means for gathering the essential developmental and clinical data with which practicing clinician can make an accurate diagnosis. These include various symptom checklists, adult ADHD and executive functioning inventories, and structured interviews that target ADHD and diagnostic criteria, including onset, course, and impairment. However, there are many other conditions that can mimic the symptoms of ADHD in adults, making it challenging to differentiate whether the “attention deficits” with which patients present actually result from ADHD or from a different condition.

The purpose of this blog is to review some of the psychiatric disorders that should be screened for during an adult ADHD evaluation, as any one of these may create “attention deficits.” Some clinically-informed tips for differentiating each of these conditions from ADHD are also provided.

Depression

         Concentration difficulties and poor initiation and follow through on tasks are characteristic features of depression, which overlap with common features of ADHD. A patient in the midst of a depressive episode will likely endorse executive functioning problems related to motivation, emotional regulation, and organization/time management difficulties. A key difference with ADHD is the course and persistence of these issues inasmuch as the executive functioning deficits in ADHD reflect a chronic developmental lag, irrespective of mood state. A thorough developmental history with self- and observer-reports assessing childhood onset and persistence of ADHD symptoms can establish if there was a history of ADHD and related problems before the onset of depression. Moreover, as depression is an episodic condition, assessment of inter-episode executive functioning helps with this differential diagnosis, as executive functioning for depressed individuals improves as depression remits. Of course, many adults with ADHD have co-existing depressive symptoms, if not a full depressive disorder in adulthood. Their executive functioning may worsen with low mood but it continues to be problematic even after their mood improves.

Anxiety

            Establishing the onset and course of symptoms is, again, key to differentiating ADHD from most anxiety disorders. For anxieties related to specific, circumscribed triggers, such as social anxiety, panic attacks, and/or phobic stimuli, any “attention deficits” associated with these anxieties should not be apparent when an anxious individual is not facing these activating events. Moreover, these sorts of anxiety disorders do not manifest in the wide ranging, cross-situational functional deficits associated with ADHD, although anxiety can be quite impairing due to its ripple effects on other domains of life, such as someone who is housebound from agoraphobia.

Anxiety is the most common co-existing diagnosis in adults with ADHD, which usually kindles and magnifies over time as patients encounter greater difficulties managing roles and obligations that increasingly require intact executive functioning. Chronic, generalized anxiety, which can develop in childhood and persist into adulthood, is often associated with distraction and avoidance that can look very much like ADHD. However, there is often less executive dysfunction for purely anxious individuals in terms of organizational and time management skills, and there is less behavioral disinhibition, as anxious individuals tend to be overly inhibited. In fact, individuals with generalized anxiety may exhibit better performance on tasks and projects once engaged in them as they represent a distraction form their worries whereas for adults with ADHD these tasks are the triggers for their anxiety.

Bipolar Spectrum Disorders

            This is one of the more challenging differential diagnoses to make, as hypomania/mania involve restlessness and impulsivity and executive dysfunction, with the corresponding depressive episodes also characterized by several ADHD-like symptoms, as was mentioned above. The different course of these disorders helps to differentiate them. The executive dysfunction and attention difficulties associated with the bipolar spectrum symptoms “ride the wave” of the prevailing mood regardless of current external circumstances. An individual in the midst of hypomania/mania has a qualitatively different presentation that is uncharacteristic of the person, such as engaging in risky activities, reporting racing thoughts, and exhibiting pressured, disorganized speech. An individual with ADHD, on the other hand, is “consistently inconsistent” such that a person has difficulties managing a variety of circumstances across time and context that transcend any mood state, and these difficulties are very familiar to the person with ADHD and those familiar with this person.

Both diagnoses are associated with sleep difficulties, although there are differences here, too. Sleep disruption in bipolar disorder is characterized by episodes (tied to hypomanic/manic episodes) of little need for sleep but nonetheless having a great deal of energy, albeit often spent on reckless or at least ill-advised actions. Adults with ADHD commonly report sleep difficulties, though more often characterized by delayed sleep onset or procrastinating on sleep despite being tired; however, unlike individuals in the midst of hypomania/mania, ADHD adults end up sleeping in too late and miss obligations, or suffer the consequences of sleep debt, such as feeling tired and fatigued, often compensating with excessive caffeine intake.

Obsessive-Compulsive Disorders

            Obsessive-compulsive disorders, and related spectrum disorders, such as trichotillomania and excoriation, involve some sort of cognitive impulse or physical urge that is associated with significant anxiety or sense of discomfort for which the individual engages in a neutralizing behavior for relief, which insidiously negatively reinforces and maintains the behavior pattern. For OCD, this might involve a mental or physical ritual when faced with feared stimuli, such as thinking through a series of prayers to counteract a “bad” thought or excessive checking to ensure an oven is turned off to counteract the feared image of returning home to find the house burned down. Skin-picking, hair pulling or other neutralizing behaviors are carried out to relieve a somatically based discomfort, such as imperfection on one’s skin or a need to feel the sensation of a hair being plucked from a follicle. These behaviors ultimately reinforce the initial impulse and maladaptive responses.

These impulses are distracting inasmuch as they chronically and significantly consume one’s attention, which may sound like distractibility consistent with ADHD, particularly for “pure obsessionals” in the OCD category. These conditions can co-exist with ADHD, often in very complex cases. A thorough developmental interview examining the age of onset and specific type of symptoms described helps to make the differential diagnosis. Structured diagnostic interviews for mood, anxiety, and other psychiatric disorders can help identify OCD and the impulse control disorders and the manner in which they create distractions and attention difficulties. The distractions are limited to these stimuli and careful probing can identify the culprit of the triggering stimuli and neutralizing behaviors, rather than the wide-ranging triggers for executive functioning problems in ADHD.

Trauma

            Persistent cognitive and emotional reactions to traumatic experiences and ongoing life disruption constitute post-traumatic stress disorder (PTSD). This and other trauma and stress-related disorders result in difficulties with concentration and memory, including a continuum of intrusive thoughts and images, and dissociative states that look like the sorts of distractibility and attention deficits seen in ADHD. However, in cases in which the onset of these difficulties can be traced to a distinct trauma (particularly early childhood trauma), PTSD is the more appropriate diagnostic formulation

This being said, not everyone who experiences a traumatic event necessarily develops PTSD. So, it is possible that in the absence of a clear trajectory of PTSD, that a course of onset of ADHD may be established. Similarly, ADHD and its executive function and motivational deficits cover a broader range of symptoms and impairments than simply attention and may co-exist with PTSD, but care must be taken to confirm these ADHD-specific features and as distinct from dissociative states or cognitive intrusions. Cases in which there is a clear developmental onset of ADHD and a trauma occurs afterwards represent another pattern of this comorbidity, such as an individual who was diagnosed with and treated for ADHD since early adolescence but has developed PTSD after suffering a serious car accident in her mid-twenties.

Summary

            The evaluation of ADHD requires at least screening for all other feasible explanations for the apparent attention deficits and other characteristic symptoms. This exercise has parallels with the “null hypothesis” in research but has important clinical implications for treatment selection. Evidence-supported treatments exist for all of the “other” conditions reviewed here and an accurate diagnosis helps direct patients to the right ones for their presentations. A clinically-informed diagnostic formulation is also essential in complex cases with multiple comorbidities to help sort through the different clinical issues, their overlaps, and to support a competent treatment plan.