In this study, we compared the psychomotor functions of adults with MDD and adults without psychiatric disorders to describe and identify the potential MDD psychomotor profile. We demonstrated the use of a standardized psychomotor examination in MDD participants. We also observed significant differences in performance between MDD and HCs on several psychomotor tasks assessing muscle tone and posture (arm dropping test; passivity; emotional control; and CORE items 2), gross motor skills (walking backward a line: time score, jumping score, and manual dexterity score), perceptual-motor skills (asymmetrical bimanual) and body image/organization (BIQ score). Patients with MDD performed worse on these tasks.
There were no group differences in physiological muscle tone (extensibility, dangling and no motor pathway disorder) or active muscler tone (synkinesia) on the muscle tone and posture tasks. However, the MDD and HC groups differed in passive muscle tone. Passivity during limbs mobilizations (passivity and intentional muscular relaxation) was challenging for participants with MDD. These individuals exhibited more paratonia and more tonic-emotional reactions (emotional control), e.g., jerky breathing and vasomotricity, during passive muscle tone tests. This difficulty in voluntarily achieving muscle relaxation was obvious on the arm dropping test, which most participants with MDD failed. The high level of tonic-emotional reactivity observed in participants with MDD contrasted with the apparent motor “passivity” evidenced by score on the selected CORE items, which were characterized by hypoactivity, immobility, lack and slowness of movement or delay in activity. Thus, an apparent psychomotor delay or slowness may mask high body tension, which can only be assessed by a clinical examination of muscle tone. Muscle tone results indicated tonic-emotional dysregulation with corporal manifestations in participants with MDD, suggesting lower emotional control abilities compared with controls. Notably, MDD is characterized by abnormalities in emotion regulation [39] and dysregulation of major biological stress systems [40],which impact personal and social aspects of lives. Both abnormalities can affect muscler tone by tonic-emotional manifestations. More generally, in human development, each emotion (anxiety or anguish) is accompanied by a tonic [41] or neurovegetative response. This interrelation between muscle tone and emotion is explained by the regulation by shared spinal and cerebral structures. A core network of cortical (prefrontal) and subcortical (various brainstem nuclei, hypothalamus, amygdala, basal ganglia, and anterior cingulate) regions involved in emotion regulation (for a meta-analysis see [42]) also participates in the regulation of muscletone. Moreover, the brainstem, in particular, is involved in the affective component of emotional responses [43]. Subcortical structures send descending projections to brainstem regions and ascending projections to cortical regions that produce the expression and affective components of the emotional response. The reticular formation in the brainstem, influenced by the basal ganglia, affects posture and muscle tone along descending projections [44, 45]. The nerve signals generated by these anatomical structures combine to deliver a message with somatic and psychic origins. Therefore, muscle tone, considered an emotional backdrop [41, 46], exhibits bodily manifestations of affective, emotional, and identity-related phenomena.
Given this interrelation between the body and a person’s affect, a psychomotor evaluation allows us to consider the "tonic dialog" [47]. The significant differences in muscle tone between the two groups and the predictives value of several muscle tone variables (passivity, emotional control, and facial immobility) for depression suggest that assessment of muscle tone indicates the states of bodily and emotional tension and should be incorporated in clinical examinations of individuals with depression.
We also found many group differences in gross motor skills, with MDD participants achieving low scores on dynamic balance (walking tests) and exhibiting major difficulties in speed of execution. This slowness in participants with MDD was also found on the manual dexterity tasks and asymmetrical bimanual praxis tasks. These results are consistent with the slowness of movement among individuals with depression described in the literature [2]. Qualitative analysis of the jumping task showed that MDD participants had more stepover jumps and less or no coordination of their arms compared to HCs, who exhibited better performance in the feet-together task for jumping and better coordination of their arms. Regarding perceptual-motor skills, MDD patients failed the asymmetrical bimanual praxis tasks, which involve coordination linked to functional efficiency of the corpus callosum, more than HCs. Contrary to the findings of Pavlidou et al. [48], we did not find significant group differences in praxis, but we did find a tendency to toward lower scores on manual gnosopraxis. The MDD and HC groups differed only on the rhythmic task. In this task, participants had to clap or walk to the rhythm set by a metronome; theMDD participants had more difficulty walking in rhythm. However, the detailed cognitive profiles of patients were unavailable in this study, and some cognitive impairments could explain their poor performance on perceptual-motor tasks.
Overall, our results showed that MDD participants were slower when performingpsychomotor tasks and that their motor participation (in the jumping and APM tasks) was weaker. Although the use of actigraphy in depression research allows for the identification of motor slowing, sometimes correlated with scales [11, 49], this method, which is rarely used clinically, does not provide objective qualitative measurements aspects of body movement and is a fragile measure of psychomotor agitation. In the present study, the clinical psychomotor approach allowed qualitative and quantitative analysis of performance. This analysis indicated that MDD did not alter global coordination but was associated with differences in execution speed and motor adaptation. The clinical psychomotor approach, with a standardized evaluation, allowed determination of specific motor and psychomotor disturbances and facilitate hypotheses as to the mechanisms involved. Quantitative assessment lacking actigraphy or instrumental measures can only screen for motor slowing or agitation without determining motor disorders, or their underlying mechanisms.
In a recent experimental study based on quantitative movement analysis, Sandmeir et al. (2021) showed that the more severe a patient’s depression was, the less body movement they exhibited. In addition, the authors found that the observed reduction in body movements was not correlated with items assessing motor symptoms on two depression scales (the HDRS and Beck Depression Inventory-II). Similarly, we found that only two psychomotor variables were related to items on the HDRS assessing motor symptoms; furthermore, the psychomotor variables were not correlated with the CORE scores of MDD patients. Other studies also failed to find a correlation between depression scales and instrumental assessments [49, 50], suggesting that the use of scales alone is insufficient for assessing psychomotor disorders.
Low body image, particularly in relation to low self-esteem, was identified in the MDD group. Apart from eating disorders, in which body image has been extensively studied, body image dissatisfaction is often found in patients with physical diseases or injuries and predicts or is associated with psychological distress (depression, anxiety, and self-esteem) or lower quality of life [51,52,53]. Any change in the body, damage or loss of function alters body image and leads to anxiety [54]. Conversely, the effect of affective disorders, such as depression or anxiety, on body image has received little attentionthus, body image in depression merits further study.
Our study showed that standardized tools specific to psychomotor examination allowed us to highlight significant differences in each of the psychomotor domains studied (muscle tone and posture, gross motor skills, perceptual-motor skills, and body image/organization) between subjects with MDD and healthy subjects. We did not highlight NSSs among patients with MDD; however, the psychomotor examination led to a neurological examination recommendation for one subject.
Several psychomotor variables were identified to predict an MDD diagnosis and merit additional investigation: body image, passive muscle tone and emotional control, gross motor skills (movement quality and speed of execution), and rhythm. To the best of our knowledge, this study is the firstto utilize standardized clinical tools specific to psychomotor functions. We demonstrated the feasibility and value of such an examination. Like Schrijvers et al. [9], we encourage the use of these specific clinical tools in a psychomotor examination carried out by trained professionals (such as psychomotor therapists and occupational therapists). Such assessments help to refine the psychomotor profile of patients, provide information on the semiology of psychomotor disorders, and provide additional psychophysiologicalinformation about depressive symptomatology.
The evaluation outlined in this study allows us to refine the psychomotor profile of patients by identifying possible disorders (psychomotor disorders and NSSs) or difficulties that may impact their daily lives. It also enables further investigation of the psychomotor semiology of depression and enabling the development of psychophysiopathological hypotheses for depressive symptoms, particularly tonic-emotional disorders. The psychomotor profile produced by the psychomotor examination should also allow clinicians to propose adapted no-drug interventions (adapted physical activity, relaxation, mindfulness, and psychomotor therapy) specific to the physical and psychomotor capacities and challenges of patient.
Limitations
The subtest from the NP-MOT battery used in this study are based on developmental psychomotor tasks that are not influenced by language or culture. However, a validation study on adults from different cultures would be of high importance given the lack of adult developmental norms. Small sample size, especially given the numbers of variables explored, was a limitation. In the future, this psychomotor examination should be conducted with a larger sample, controlling treatment and cognitive affection, to confirm the results of this study.
Expansions
We did not find any evidence of cognitive impairment in the study participants, although cognitive impairment may be associated with depressive disorders [55, 56]. We were therefore unable to compare the psychomotor profiles of participants with and without cognitive impairment. However, only five out of 25 participants with MDD were identified as exhibiting significant psychomotor retardation according to the CORE scale. In a future study, it would be interesting to include MDD participants with associated cognitive impairment and/or psychomotor retardation, as identified by clinicians to determine if psychomotor profiles differ according to these clinical characteristics.