Although rarely seen, the spectrum of psychosomatic manifestations of patients with brucellosis is very diverse, and many authors presented cases with mental disabilities that ranged from subtle cognitive dysfunctions detected only by neuropsychological evaluation to apparent psychosis or schizophreniform disorders. The psychiatric manifestations, while rarely reported, were depression, amnesia, agitation, nightmares, personality disorders, euphoria, nervousness, loss of perception, disturbance of spontaneous and voluntary attention, disturbances in process of thinking with poverty of content, hallucination, delirium, convulsion, dysarthria, psychosis, and night raving [14, 17, 23, 30]. In a study by Shehata et al. [35], 38.5 % of patients with brucellosis without apparent neurological symptoms had depression or cerebellar affection, in addition to significant impairments in some cognitive function, as mental control, logical memory, and visual reproduction in comparison with control group. In this study, depression was detected in seven patients (29.2 %); three of them have evident neurobrucellosis, whereas four were apparently without any neuropsychiatric involvement [35]. Depression is significantly more present in patients with brucellosis without marked neurological symptoms than in patients with apparent neurological manifestations. The explanation of that could be relied on the mechanism of depression in these patients whose altered moods point to different mechanisms such as direct effect of the organism or its products on the meninges and brain [1, 35]. Alapin [2], in his extensive review of neurological aspects of brucellosis, wrote that “many papers underline the commonness of neurological and psychotic complications with infection by B. melitensis. There is an option that B. abortus produce a much lower percentages of neuro-psychiatric complications than B. melitensis or B. suis” [2, 38]. Roger and Poursines [31] classified the neuropsychiatric manifestations of brucellosis as “psychotic encephalitis of the pseudo-tumoral form” and “different psychological disorders” with psychasthenia as the most common form for a late course of chronic brucellosis.

According to Alapin [2], multiple cases were diagnosed as neurasthenia, psychasthenia, or depression during the course of chronic brucellosis without an acute period. Evans [15] called this state “a ramshackle feeling” (in French: patraquement) and Janbon and Bertrand “subjective syndrome of chronic brucellosis.” Those subjective symptoms were headaches, tiredness/fatigability both physical and mental, insomnia in the evening as well as early awakening, increased nervous sensibility, sexual troubles, as well as pains and aches without easy explanation. Those symptoms sometimes increased to complete psychic asthenia, incapacity of concentration, troubles of memory, irritability, exaggeration of emotions, and depressive states. Such a state is much more expressed in persons who, even before infection, showed immaturity or inadequacy of personality [2].

While these authors represented depression as the most common manifestation of brucella mental disturbances, some like Imboden believed that depressive mood is part of a fatigue syndrome accompanied by any chronic illness rather than a specific representation of neurobrucellosis, which manifests significantly more often in cases who suffer from other psychological traumatic experiences and personality or mood disorders. In one study, he compared eight patients with brucellosis who had recovered in 2 or 3 months, with 16 who were still symptomatic after 1 year with such complaints as fatigue, headache, nervousness, and vague aches and pains. All, but one, were males. There were no differences between the two groups in medical findings at onset or at time of reexamination. The 16 who were still ill, however, differed significantly from the eight who had recovered with respect to incidence of psychologically traumatic events in early life (69 % vs. 25 %), a seriously disturbed life situation within 1 year before or after the acute infection (69 % vs. 0 %), and significantly higher scores on an index of morale loss derived from the Minnesota Multiphasic Personality Inventory (MMPI) [21]. He described a patient who was visited 2 years after a treated acute brucellosis. He was an emigrant who suffered from depression, extreme fatigue, headaches, introversion, and asociality. His younger siblings were dead, and his parents left him alone and returned to their homeland before his illness. Another patient with the diagnosis of chronic brucellosis and symptoms of depression and lassitude was a heavy drinker who became a member of a religious order after his father died. His mood disorder did not improve even after the successful treatment of brucellosis. The authors debated whether these disturbed life-associated mood disorders were related to the diagnosis of brucellosis [25]. Conversely, Eren et al. [14] studied 34 neurobrucellosis cases and 30 patients with brucellosis without neurological involvement. The patients were evaluated by two psychiatrists, and the Hamilton Depression Rating Scale (HDRS) and Mini-Mental State Examination (MMSE) or Folstein tests were performed before the therapy and 1 and 2 weeks after the therapy. The psychiatrists interviewed the neurobrucellosis patients and diagnosed mild depression due to a general medical condition (neurobrucellosis) according to DSM-IV criteria in all of the cases. The mean score of MMSE among neurobrucellosis patients was 21.7 before the therapy. The improvement began in the first week of the therapy and reached a mean score of 24.3 at the end of the second week (p ≤ 0.001). The mean HDRS test score among neurobrucellosis patients was ten before the therapy and improved to 8.2 1 week later (p = 0.006) and to 5.2 2 weeks later (p = 0.001). On the other hand, among the brucellosis patients without neurological involvement, no significant changes of MMSE and HDRS test scores were observed. The test scores of neurobrucellosis patients were also compared with the scores of the patients without neurological involvement before the therapy. Test scores of HDRS were significantly different in two groups (p = 0.035), whereas test scores of MMSE were not (p = 0.351). They also found that the improvement in the MMSE scores in neurobrucellosis was significant (p ≤ 0.001), whereas in control group, it was not. The mild depression that was detected in neurobrucellosis patients after the psychiatric examination was improved at the end of 2 weeks (p = 0.001). On the other hand, among the brucellosis patients without neurological involvement, depression was not detected as HDRS test scores were within normal ranges. The significant difference between the HDRS scores in two groups (p = 0.035) supports the depression seen in neurobrucellosis. While no improvement of the scores was noticed among the patients without neurological involvement, the authors concluded that the cognitive and emotional disturbances among neurobrucellosis improve by antibiotic therapy, without any antidepressive or antipsychotic therapy [14]. Finally, it seems that although previous traumatic stress disorders during childhood as well as the current life-disturbing events can affect the extent and severity of the mood swings in brucella patients, the deleterious impact of the infection itself on their psychological symptoms and mental disabilities is a matter of serious concern.

A wide variety of psychiatric symptoms ranging from memory deficits and mild personality changes to severe depression and frank psychosis have been described in patients with brucellosis. Alapin [2] claimed that the difference in severity of cases is due to such pathogenetic factors as extreme virulence of Brucella spp., constitutional somatopsychic predisposition of individuals, and the time of exposure to infectious process.

Almost all authors have pointed out that neuropsychiatric manifestations of brucellosis can display in every stage of the disease: as a presenting symptom in acute brucellosis [32], during the exacerbations mostly with febrile course [32, 38], or in chronic course, mainly many years after infection [2].

Alapin [2] presented two interesting cases with active brucellosis and paranoid personality disorder, which had persecutory delusions:

“He showed confusional state, was agitated, expressed multiple persecutory delusions and several ideas of reference (“they think that I am a Nazi … I am followed . . . trains were stopped to prevent my being on time”, etc.). During further observation he became lucid and then he was able to explain that during the acute phase he had visual and auditory illusions and hallucinations. The delusional syndrome slowly receded when treated with chlorpromazine but returned later … The CSF was normal and the electroencephalogram (EEG) showed rather a normal trace. The diagnosis of brucella encephalopathy with chronic paranoid psychosis and brucella peripheral poly-neuropathy was made.”