Sexual obsessions are shown to be included onto the “unacceptable/forbidden thoughts” category [1, 2] and may comprise ego-dystonic, intrusive, recurrent and persistent thoughts, images or concerns about sexual matters that do not usually prompt sexual behavior. Thus, sexual obsessions can be considered a form of obsessive compulsive disorder (OCD) themselves .
The latent symptom structure of OCD was best defined by four specific dimensions: (a) obsessions and checking (e.g., aggressive, sexual, religious, and somatic obsessions and checking compulsions); (b) symmetry and ordering (e.g., symmetry and exactness obsessions, repeating, counting, and arranging compulsions); (c) contamination and cleaning (e.g., contamination obsessions and cleaning/washing compulsions); and (d) hoarding . In patients with OCD, obsessions and checking were found to be more diffuse (92.78%) and associated with a greater overall functional and lifestyle impairment than other categories of symptoms .
In this study, we focused only on sexual obsessions, since the severity of obsessions, but not compulsions, was found to be related to impairment across several domains of life [5, 6].
The literal content of sexual obsessions may resemble other types of iterative sexual ideation, as seen in paraphilia, post-traumatic stress disorder, and normal sexual fantasy of the general population. Intrusive thoughts are frequently reported by nonclinical samples of adults (80%–88%) . However, most people are able to dismiss them, whereas clinical sexual obsessions are perceived as personally significant, upsetting, and relentlessly recurrent . Patients who experience such a type of “pure obsessions” (i.e., obsessions that are often characterized by the absence of overt compulsions) appraise intrusive thoughts as dangerous and overly important and, thus, struggle to control their thoughts . Therefore, these patients feel greater distress about unacceptable thoughts than nonclinical populations in terms of the extent of distress, frustration, time lost, and impairment .
Sexual obsessions are common symptoms among OCD patients, with prevalence of 13.3-24.9%,  and 30.2% in combination with religious obsessions . Hasler et al.  found that people with certain sets of OCD symptoms were more like to have certain comorbidities than others. In particular, about 82.1% of OCD patients with sexual obsessions was found to have a comorbid Axis I diagnosis . OCD and depressed patients were found to have in common some dysfunctional appraisals about their most disturbing obsessions: guilt, unacceptability, likelihood thought would come true, danger, and responsibility for having the intrusive thoughts . Other studies have related bipolar disorder to this cluster of symptoms  highlighting the need of further studies if we consider that these patients, besides depressed ones, often report sexual dysfunctions and these are associated with increased suicidality . Although these are not uncommon symptoms, the topic of sexual obsessions as a psychiatric symptom and the presence of sexual obsessions within patients with a primary psychiatric diagnosis other than OCD have not been well researched.
In schizophrenia, obsessive compulsive symptoms were reported by 10%  to 26.7% of patients, the frequent obsessions being that of contamination, sexual and aggressive thoughts . Although OCD co-occurs in a substantial proportion of schizophrenia patients , the rate of occurrence and the clinical effect of sexual obsessions have been scarcely investigated in these patients. Even though the rate of sexual obsessions was not investigated, 23% of patients with a diagnosis of panic disorder were also found to have general obsessive compulsive symptoms .
Gender is a relevant factor that should be taken into account when evaluating patients with obsessive symptoms, as a significantly higher frequency of sexual obsessions was observed in males than in females .
People with OCD feel a great distress about unacceptable thoughts, to the point that some studies found an association between obsessive compulsive spectrum and suicidality [22, 23]. Suicide is defined as the act of intentionally ending one's own life. Its immediate precursors are suicidal behaviors that include suicidal ideation, plans, and attempts . Suicidal ideation consists of thoughts about suicide, which varies greatly from a desire to be dead (passive) to a formulation of intent (active). Suicidal plans refer to making detailed plans to commit suicide, without the suicidal act itself. A suicide attempt consists of a failed act of suicide. The estimated lifetime prevalence of suicidal ideation, plan and attempt in a large overall cross-national sample (N = 84 850) was 9.2%, 3.1% and 2.7%, respectively .
Recently, the severity of obsessive compulsive symptomatology, the presence of major depression and aggressive obsessions, and high levels of anxiety or hopelessness have been suggested that could lead patients to consider or attempt suicide to escape from their distressing symptoms .
Suicidal behaviors were found to be more common in patients with mood disorders than in other psychiatric disorders, followed by patients with anxiety disorders and impulse-control disorders . Suicidal behaviors are also a frequent complication of schizophrenia with prevalence ranging between 20% and 40% [26–28]. Nevertheless, features of suicidality in schizophrenia patients remain poorly understood .
In summary, a large literature indicates an association of OCD and other psychiatric disorders with suicidal behaviors. A much less extensive but consistent literature indicates comorbidities between OCD and other psychiatric disorders. Nevertheless, the influence of subtypes of OCD, such as sexual obsessions, on suicidal behaviors, in patients with a psychiatric diagnosis, was scarcely investigated. A recent study  is the only one published article addressing this issue. Results indicated that 36% of patients with OCD reported lifetime suicidal thoughts, 20% had made suicidal plans and 11% had already attempted suicide. In this sample, variables associated with lifetime suicidal thoughts and plans were socio-demographic variables (lower social class, not having children, and religious practice), comorbid mental disorders (major depression, posttraumatic stress disorder, substance use, and impulse-control disorders) and sexual/religious obsessions . Suicide attempts were predicted only by mental disorders.
The purpose of this study was twofold:
To estimate the lifetime presence of sexual obsessions and suicidal behaviors in patients with primary diagnoses of mood disorders (major depressive, dysthymic, and bipolar disorders), panic disorder, and schizophrenia, and in a sample of subjects without any psychiatric disorder;
To investigate the possible effect of socio-demographic factors, mental disorders and sexual obsessions on suicidal behaviors.