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Attention can directly influence sensory cells. For example, attention can influence the activity of sensory hairs in the ear. It therefore stands to reason that perceptual symptoms in ADHD are not only influenced by inadequate filtering of incoming sensory stimuli, but also at the level of activation and alignment of the sensory cells1
8.1. Increased sensitivity / stimulus filter too wide open¶
In the following, we speak of heightened sensitivity. In contrast, high sensitivity is a construct by Aron (validated only to a limited extent to date) that contains other elements in addition to increased sensitivity (in particular a certain form of perception/perception processing), which does not play a role here.
A Korean study found increased sensitivity (SOR) in 18% of all children and in more than 50% of all children with externalizing or internalizing disorders2
The function of dopamine in the brain is to “de-noise” transmitted signals, i.e. to suppress irrelevant signals. ADHD is associated with a lack of dopamine. It is therefore not surprising that ADHD is associated with increased perception (in the sense of increased permeability) of irrelevant signals, which is reflected in increased distractibility on the one hand and increased perceptual sensitivity on the other.
8.1.1. Increased sensitivity / stimulus filter too wide open as an ADHD symptom¶
Openness to stimuli3 is a symptom of ADHD4, which has sometimes also been called stimulus filter weakness. However, this term only refers to one part of ADHD.
Maladaptive reactivity to sensory input is frequently observed in neurodevelopmental disorders such as ADHD or ASD.56
People with ADHD suffer from overload (overstimulation in the sense of sensory overload) - they perceive incoming stimuli, especially visual, acoustic and tactile stimuli, to an increased degree. They are so overwhelmed by normal environmental stimuli that they are unable to filter out background noise7
Lachenmaier’s filter model is very helpful in understanding the effects of the missing stimulus filters.8
ADHD is almost always accompanied by increased sensitivity. In our ADxS online symptom test, 87% of 200 diagnosed people with ADHD showed signs of increased sensitivity. This corresponds roughly to the value for attention problems, so it is very high. Increased sensitivity is an increased intensity of perception. Other studies also found a correlation of increased sensitivity with ADHD symptoms9 and also with lower quality of life,10 whereby increased sensitivity in ADHD is often associated with comorbid ODD or anxiety and exists regardless of the subtype.11 An evaluation of almost 1900 data sets of the ADxS online symptom test (as of June 2020) also found that increased sensitivity correlated to the same extent with ADHD-HI as with ADHD-I. Interestingly, another study found a correlation of SOR (Sensory-Over-Responsivity) in ADHD with an increased cortisol stress response (which we believe is more common in the ADHD-I subtype), while non-SOR ADHD people with ADHD showed a flattened cortisol stress response (which we believe is more common in ADHD-HI). SOR was not associated with certain externalizing behaviors, but was associated with avoidance of sensory stimuli.12 Another study also found increased sensitivity in adult persons with ADHD.13
ADHD shares with increased sensitivity the stimulus filter that is too wide open, probably controlled by the thalamus.
Examples:
Light sensitivity
Visual sensitivity
Noise/noise sensitivity
Acoustic sensitivity
Jumpiness
Emotional sensitivity
The feelings of others are transferred to you
Feeling the moods of others unpleasantly intense
Movies
Can easily make you cry
Don’t like watching (certain) movies because the sensations are too intense
Perceive tastes / smells more intensely
Olfactory sensitivity
This is said to correlate (independently of ADHD) with an increased sensitivity in the selection of preferred foods14
Tactile sensitivity
Rough fabrics are unpleasant
Temperature sensitivity
Particular sensitivity to high or low temperatures
Want to change the temperature earlier than others
Hypoglycemia / hunger / thirst is difficult to bear
Sensitivity to pain
Rarer than other features
In particular, increased tactile sensitivity in ADHD is said to correlate with increased anxiety.15 A correlation was also found between SOR and anxiety.16
Around half of all people with ADHD also fulfill the criteria of the Sensory Over-Responsivity Test.1715 It has been hypothesized that SOR could correlate with a GABA deficiency
Compared to non-affected individuals, children with both ADHD and ASD showed increased stimulus sensitivity. While ASD showed higher auditory stimulus processing than ADHD, ADHD was associated with higher visual stimulus processing than ASD. Sensitivity to stimuli decreased with age in all groups. ADHD was found to have deviant patterns of perception and processing of sensory stimuli:18
Tend to search for sensory input (search pattern)
Are more aware of sensory stimuli (sensory patterns)
Are more easily disturbed by certain stimuli (avoidance patterns)
Perceive sensory stimuli more weakly (lower registration/attendant pattern)
Children with ADHD show increased sensory sensitivity and have problems with proprioception, vision, auditory and tactile sensory processing. These sensory processing deficits are associated with functional, social, behavioral and learning difficulties.19
8.1.2. Increased sensitivity and correlation with ADHD subtypes¶
According to the evaluation of almost 1900 data sets of the ADxS.org symptom test, increased sensitivity correlates equally highly with ADHD-HI and ADHD-I (0.50 to 0.51). Looking at the individual sub-areas of sensitivity separately, there are indications of different correlations with the subtypes:
Sensitivity sub-area
Correlation with ADHD-HI and ADHD-C
Correlation with ADHD-I
Light sensitivity
0.20
0.41
Noise sensitivity
0.22
0.34
Startle response
0.20
0.25
rough materials unpleasant
0.18
0.20
The mood of others is transmitted
0.28
0.25
Temperature sensitivity
0.21
0.11
Not being able to ignore conversations at the side table
0.35
0.30
Can’t ignore the TV in a pub
0.40
0.29
Total distractibility (for comparison)
0.50
0.38
Limitations:
The question on temperature sensitivity was aimed at whether the respondent was one of the first to want a change in temperature. In addition to the feeling, this also includes the willingness to make the statement, which is likely to influence the result. This is a non-validated online self-test (screening).
A (stress-related) increase in noradrenaline levels directly triggers increased perceptual sensitivity.20 The increase in noradrenaline is mediated by the nucleus coeruleus.21 The nucleus coeruleus is activated by stress (among other things) and in turn activates other stress systems such as the sympathetic nervous system.22 Increased sensitivity is therefore also a possible symptom of stress.23
Empathy is the ability to empathize and understand the feelings and experiences of others. The multidimensional empathy concept distinguishes between cognitive empathy (understanding the emotional states of others, similar to the Theory of Mind) and emotional empathy (the emotional reaction to the emotional state of others).27 The third element is emotion recognition, see there.
There are various concepts that describe how empathy arises.
Comorbid PTSD or intrusions can reduce cognitive empathy. 27
Emotion recognition is a sub-area of empathy28 and refers to the ability to recognize emotions based on language, facial expressions or behaviour.29
In ADHD (as in autism), there appears to be impaired recognition of the emotions of others, although stimulus processing is impaired at a different processing level than in ASD.303132 In addition, many people with ADHD have considerable difficulties in recognizing and controlling the expression of their own emotions.33
Emotional dysregulation in ADHD can be caused by deficits in recognizing and / or assigning emotional stimuli.34
People with ADHD are less able to recognize emotions in faces.35 Children with ADHD, ASD or language development disorder showed a similar developmental delay in their ability to recognize emotions.36 A meta-analysis confirmed a deficit in the recognition of facial expressions (Facial Expression Recognition Deficit, FER) in ADHD. This also occurs in ASD, borderline, Parkinson’s and schizophrenia.37 Boys with ADHD showed deviating brain activity when perceiving the faces of family members.38ADHD correlated with greater activation of the right nucleus accumbens in the perception of fearful and happy faces.39
A meta-analysis found in 16 of 17 studies that ADHD children and adolescents show difficulty processing emotional information conveyed by visual scenes.40
The fact that the perception of emotions in faces shown seems to be altered in people with ADHD, even if the persons with ADHD are no longer diagnosed with ADHD in adulthood,41 could be an interesting aspect of the change in empathy in ADHD
Similarly, people with disorganized attachment styles showed a reduced ability to read emotions from faces, which correlated more strongly with ODD than with ADHD. This also correlated with increased emotional reactivity.42 This is somewhat similar to a pattern known in borderline
This seems to contrast with our data from the ADxS.org symptom test on the question “Do you sometimes find the moods of others unpleasantly intense?”, which was answered in the affirmative significantly more often by people with ADHD than by those without. On a 5-point scale (-2 quite a little, -1 rather a little, 0 neither, 1 rather clearly, 2 quite clearly), people with ADHD achieved an average score of 1.0, while people without ADHD achieved an average score of 0.4 (n = 1889, as of June 2020). On closer inspection, however, a distinction should be made between the ability to recognize the emotions of others and the ability to distance oneself from the emotions of others (which is the aim of the symptom test question).
One study found a reduced capacity for empathy in people with ADHD.43 In their self-perception, people with ADHD report an increased and sometimes excessive capacity for empathy.44
In ADHD, the ability to empathize may often be impaired. However, it is not fundamentally non-existent, which distinguishes ADHD from psychopathy
Rather, it seems that people with ADHD are often unable to access or use their empathic ability. Since empathy, like attention (see there), follows motivation or is at least regulated by it4546 , it seems conclusive to us that in ADHD it is not so much empathy per se that is impaired, nor the ability to control empathy (the “technical” ability to direct empathy), but rather that the control profile that directs empathy through motivation is impaired or inappropriate, as is also the case with attention.
The fact that the ability to empathize is not non-existent in ADHD, but rather buried, is shown in 1:1 encounters in a quiet environment or in hyperfocus - e.g. when in love. People with ADHD-HI and ADHD-C are also described as very charming, empathic and accommodating. This may have a different effect on individual people with ADHD, especially those with an existing comorbidity from the aggression spectrum. However, this appears to be due more to the comorbidity.
There are reports of conspicuously high μ-frequencies in the EEG of people with ADHD.47 This high activity of brain waves in the μ-frequency range is representative of an underfunction of the mirror neurons, which are responsible for the ability to empathize with a counterpart. The phenomenon of a lack of μ-frequency suppression when observing others also occurs in autistic people (mirror neuron hypothesis).48
μ-rhythms can be suppressed by clenching the fist. So far, however, fist clenching has not been observed to influence empathic ability in ADHD or in non-affected individuals. Therefore, μ-frequency activity appears to be correlated rather than causally related to empathic ability. In addition, the data from the ADxS.org symptom test show that the statement “Moods of others are transferred to me” is significantly more common in ADHD than in non-affected people. This also contradicts the assumption that the ability to empathize is impaired in ADHD.
8.2.3. Empathy impaired - especially in ADHD-HI subtype?¶
It therefore seems to be less due to a lack of “technical” ability to empathize, but rather to the fact that the exercise of empathy is buried by other things (inner restlessness, sensory overload). Nevertheless, a reduced exercise of empathy is a symptom that frequently occurs in ADHD. We have the (subjective) impression that reduced empathy (exercise) is more common in people with ADHD-HI and increased empathy is more common in people with ADHD-I. Hyperactive/impulsive people with ADHD-HI and ADHD-C often appear less empathic to the outside world. It is certain that ADHD is almost always associated with increased sensitivity. In our online study, we found signs of increased sensitivity in 87% of 200 diagnosed people with ADHD. This corresponds roughly to the value for attention problems, so it is very high. Increased sensitivity is a more intensive perception of external stimuli. Empathy is the ability to put oneself in the shoes of others and to understand or sympathize with their feelings (cognitive empathy) and the ability to sympathize with these feelings (emotional empathy). The data on the correlation of individual parts of increased sensitivity with the ADHD subtypes (see above under Increased sensitivity) indicate that the statement “The moods of others are transferred to me” applies significantly more strongly to those with ADHD than to those without, whereby this even affects the ADHD-HI subtype a little more than the ADHD-I subtype, which could indicate that the subtypes have at least the same level of empathy.
The worse off a person is, the higher their inner tension or anxiety, the higher the stress level, the lower the empathy shown.49 This could be seen as a fairly healthy stress reaction: When it comes to survival, everyone is out for themselves. Once the stress and anxiety are gone, it is possible to empathize with others again. Findings that a blockade of glucocorticoid receptors increases empathy also point in this direction.50 In conjunction with a study in which children with ADHD showed a flattened cortisol response to the TSST, the stronger their psychopathic traits (callous unemotional traits = CU traits) such as lack of empathy, emotional coldness, etc., the lower their cortisol response. 51 and other studies that also found a correlation between callous unemotional traits and externalizing symptoms5253 or impulsivity54 in ADHD, suggest that a flattened cortisol stress response, which is common in ADHD-HI, is associated with a lower capacity for empathy, so that a distinction should be made between the subtypes.
The permanently persistent inner overactivation in the ADHD-HI and ADHD-C presentation forms, the permanent inner restlessness (which, according to the data of the ADxS online symptom test, is reflected in a strongly impaired ability to recover in ADHD-HI, which is also increased in ADHD-I compared to non-affected people, but not as much as in ADHD-HI) seems to demand so many resources from people with ADHD that they can barely exercise their ability to empathize - which is actually present, although sometimes untrained due to lack of use. People with ADHD-I, on the other hand, seem to be able to exercise their empathic abilities to a particularly high degree. It is conceivable that this is less a Consequences of different personality aspects in ADHD-HI and ADHD-I, but rather that this results from the fact that ADHD-HI is characterized by a chronically activated HPA axis (due to a lack of ability to recover due to a typically flattened cortisol stress response, which is no longer able to shut down the HPA axis), while ADHD-I is characterized by an excessive endocrine stress response, whose high cortisol stress response reliably shuts down stress-induced activation of the HPA axis. According to our understanding, these endocrinological patterns could possibly explain a different frequency of empathy in ADHD-HI and ADHD-I.
This is in line with research findings on PTSD/PTSD, which indicate that communication between the cerebral hemispheres is essential for recognizing and processing emotions. This communication between the cerebral hemispheres is functionally disturbed in PTSD/PTSD without any anatomical interruption of communication, as is the case in epilepsy when the corpus callosum is severed as a last resort, which also leads to alexithymic (emotionally blind) behavior.55 In states of strong emotional or cognitive stress, events in the right hemisphere are also functionally separated from the left hemisphere in neurologically intact people by inhibiting transmission between the brain hemispheres 56
Furthermore, early childhood stress is probably associated with reduced emotional empathy, but not reduced cognitive empathy.57
The fact that acute pain tends to increase empathy could be an interesting aspect in relation to self-harm behavior in borderline patients.5859 A distinction could then be made between short-term stress (increasing empathy) and chronic stress (decreasing empathy). Empathy is also increased in rats under low acute pain stress, while it is reduced under severe pain stress.60
See also: Brain hemispheres in ADHD.
8.3. Time perception problems with ADHD (chronasthenia)¶
In ADHD, the perception of time is very often disturbed.
Barkley61 sees time perception problems as a separate and significant symptom of ADHD. Studies report that people with ADHD are less able to estimate how long they need to complete a task - and consequently what they can accomplish within a given period of time. This normalizes under medication.62 No differences were found between the ADHD subtypes.63 Time perception and time processing problems affect children and adults with ADHD64 and are already an indication of possible ADHD in preschool children.65
Time perception problems often result in a frustratingly negative perception of one’s own performance, which could at least partly be a consequence of a faulty perception of time. This in turn reinforces a negative self-perception. (See also: Performance problems as an ADHD symptom)
Changed perception of time as a stress benefit?
A changed perception of time could represent a stress benefit. In acute danger, it makes sense to prioritize things that are not essential for survival as less important. A change in the perception of time could support the prioritization of things that are necessary for survival. Find out more at ⇒ Stress benefits - the survival-promoting purpose of stress
An individual who is in acute danger (survival-threatening stress) has a greater chance of survival if he or she treats all distant things as less important and all immediate things as more important. Since everything that is further away is not as important in the emergency mode of the survival assurance program, it could also be less important to be able to accurately estimate the temporal distance and the time required for tasks that are further away.
Time understanding of highly industrialized countries as a contributory cause?
Rossi66 notes that the understanding of time in highly industrialized countries is very strict for cultural reasons. Even in highly developed Mediterranean countries, one encounters a different understanding of time than in Germany or the USA. This is all the more true for large parts of the world. He therefore questions whether this is really already a pathological symptom.
However, since it has been empirically proven that people with ADHD have significantly more time perception and scheduling problems than other members of the same cultural group, the phenomenon is definitely a relevant ADHD problem and not a question of cultural fit ADHD also occurs in the countries mentioned by Rossi with such a different perception of time.
At the same time, Rossi himself mentions a lack of sense of time as a symptom of ADHD-I (without hyperactivity).67
With ADHD, the ability to estimate how much time an action or task will take is limited.686970
Persons with ADHD are less good at estimating longer time intervals than people without ADHD.
Forms of appearance:
Completing work too late
Constantly arriving late
Multiple causes:
Time estimation error
Waiting is unbearable (Delay Aversion)
Waiting is rest and inactivity (with the Consequences of dysphoria during inactivity)
Every living being is driven by the desire to maintain the best possible mood
The time until X is fully utilized for activities. As something usually goes wrong and time estimation is a problem with ADHD, people with ADHD are often late. It is better to do this or that quickly than run the risk of arriving too early and then having to wait. This results in frequent tardiness.
Now is always
The perception of what is important has shifted towards the present
Time passes extremely quickly for interesting things / work
Others are kept waiting
Consequences are that others feel disrespected (even if this was not the motive of the person with ADHD) and understandably react with rejection. This triggers the already miniaturized self-esteem of the person with ADHD.
In order to distinguish the length of two time intervals, one of which lasted 1 second, the other had to last 1.184 seconds for people without ADHD, while for people with ADHD it had to last 1.238 seconds and thus be 30% longer.71 Other studies have come to similar conclusions.72 In ADHD, the ability to reproduce a time interval of the correct length is also impaired. This impairment correlates with impulsivity.73 Both tonic and phasic dopamine levels (measured using the beta power before the start of the interval) correlate with performance in timing. Dopamine plays an important role in interval timing even in the range of naturally occurring fluctuations.74
Time perception in ADHD focused on the present and positive future?
8.3.3. Time perception in ADHD focused on the present / positive future?¶
There are still too few studies on this aspect to be able to make a reliable statement in relation to ADHD.
A number of studies have focused on individual differences in the perception of time, in particular the distribution of attention to time perspectives such as the future, past and present.75 One standard for assessing time perspective is the Zimbardo Time Perspective Inventory (ZTPI). The ZTPI estimates the intensity with which perception focuses on the past, present and future and whether the time perspective tends to be perceived positively or negatively.62 Various types of disorders can be attributed to imbalances in the perception of time.
As mentioned at the beginning, there are still too few studies on this aspect in relation to ADHD to be able to make a reliable statement.
One (as yet unverified) thought is that an altered perception of time in the sense of a focus on the present (in the sense of a perceived “now is always”) could intensify the subjective perception of stress through increased helplessness. If there is no perspective that an unpleasant condition, a pain, will also pass again, this is likely to significantly increase the subjective stress caused by this perception. This could help explain the increased subjective perception of stress in ADHD.
8.4. Chronic pain, increased sensitivity to pain in ADHD¶
People with ADHD often show increased sensitivity to pain. High ADHD scores correlated with increased pain82
Similar symptoms are increased sensitivity to stress and increased sensitivity to punishment. See also Emotional dysregulation.
Of 100 women with ADHD or ASD, 76% reported chronic pain.83 Chronic widespread pain (CWP), the main symptom of fibromyalgia, was almost twice as common in ADHD (39%) as in ASD.
The most frequently mentioned painful areas of the body were
Lower back (47 %)
Neck (37 %)
Shoulder (35 %)
Head (32 %, related to ADHD)
Stomach (30 %)
Arms / hands (30 %)
Upper back (27 %)
Knee (27 %)
Hip / thigh (18 %)
Calves / feet (16 %)
Breast (4 %)
Pain is associated with reduced tonic dopamine firing, which causes increased phasic dopamine firing in the nucleus accumbens.84 This is consistent with Grace’s model of decreased tonic and increased phasic dopamine firing in ADHD. See also Tonic and phasic dopamine in explanatory models for ADHD In the section Dopamine in the chapter Neurological aspects.
People with chronic pain show reduced responsiveness within the mesolimbic dopamine system to meaningful stimuli, reduced D2 receptor binding, reduced presynaptic dopamine activity in the striatum at rest and after an acute pain stimulus.85 In animals, chronic pain leads to decreased c-Fos activation in the VTA, decreased total dopamine levels and decreased D2 receptors in the striatum.85
Conversely, a reduction of dopamine in the brain by acute depletion of the dopamine precursors phenylalanine and tyrosine caused increased subjective pain sensitivity (the degree to which pain was perceived as unpleasant) without altering the sensory perception of pain.86
Increased pain sensitivity was found in 6-OHDA mice, in which dopamine synthesis is chemically damaged, making them an ADHD animal model. The pain sensitivity was presumably mediated by α- and β-adrenergic and D2/D3 receptors. Atomoxetine87 such as MPH88 was able to reduce the increased pain sensitivity in ADHD.
Stimulation of the substantia nigra, one of the two most important sources of dopamine in the brain, causes pain relief by activating spinal cord neurons via dopaminergic signaling pathways.899091 Painful stimuli cause a release of dopamine in the dorsolateral striatum, which correlates with the subjective perception of pain intensity. The ventral striatum is also clearly associated with the emotional dimension of the human pain process and the expectation of pain.92
In Parkinson’s disease, which is also characterized by dopamine deficiency, 30 to 50 % of people with ADHD suffer from increased sensitivity to pain.93 This can be improved by dopaminergic medication94, e.g. levodopa or deep brain stimulation.95
Conversely, the perception of pain is reduced in schizophrenia, which is associated with increased dopamine levels.96
MPH can remedy the increased sensitivity to pain in people with ADHD.979899100
