Aggression is any form of behavior, from physical violence to verbal threats, that involves attacking another person, living being or object with the intent to cause harm, pain, or injury. It represents a major public health issue as it affects individuals of all ages and, according to some estimates, accounts for up to 1.3 million lives globally each year. Aggressiveness is most commonly divided into proactive or instrumental and reactive or impulsive aggressiveness. When an individual is proactively aggressive, it means that their aggressive actions are premeditated and cold-bloodedly executed to achieve a certain goal. On the other hand, reactive aggressiveness is usually a response to provocation or a stimulus perceived by the person as dangerous or threatening; it is thus unplanned, impulsive, and accompanied by activation of the autonomic nervous system. There is no simple answer to the question of why someone behaves aggressively: numerous factors can precipitate aggressive behavior and lead to inappropriate actions or reactions in an individual. There is no doubt that in some individuals, the basis for violence is neurobiological. Brain regions responsible for behavior, control of reactions, emotions, and decision-making based on consequences are most often considered in this context: the ventromedial (vmPFC), ventrolateral (vlPFC), and dorsolateral (dlPFC) prefrontal cortex; the anterior cingulate cortex (ACC) and insular cortex; and structures of the limbic system, primarily the amygdala and hippocampus. Neuroimaging studies continuously show volumetric and functional anomalies in these regions in violent individuals and incarcerated offenders. Furthermore, there is increasing research attempting to link certain genes with increased aggressiveness. Genes encoding enzymes responsible for the breakdown of catecholamines, primarily the gene for monoamine oxidase A (MAO-A) and catechol-O-methyl transferase (COMT), stand out in this field. Additionally, genes related to the serotonergic and dopaminergic systems, as well as other neurochemical factors such as glutamate, GABA, orexin, oxytocin/vasopressin, opioids, and many others, are being investigated. It is believed that genes alone are not solely responsible for certain behaviors in humans; environmental factors also have a significant influence on them. Early childhood experiences such as neglect, violence, parental addiction, and criminal history, as well as substance abuse in adulthood, are particularly notable among these factors. Certain traumas, neurodegenerative or malignant brain diseases can also cause behavioral changes in previously unproblematic individuals. Psychiatric disorders, primarily schizophrenia spectrum disorders, personality disorders, but also other psychiatric diagnoses such as bipolar affective disorder (BAP) or post-traumatic stress disorder (PTSD), carry a certain risk of aggressive behavior or committing a violent crime. The relative risk that a psychiatric patient will commit any type of violent act is two to four times higher than for a person without a psychiatric diagnosis, although the absolute risk in the general population is low. This information is important from a medical, public health, and legal perspective. Firstly, there is a stigma towards psychiatric patients in society, and unselective media reporting often fuels this fear. The assumption that a patient might behave aggressively shapes the therapeutic approach, especially during hospitalization. Additionally, a psychiatric diagnosis and possible insanity at the time of committing a violent crime affect the court verdict and penalty for that crime, and recognizing risk factors serves to protect the patient themselves, those around them, and the general population, enhancing the quality of life and safety for all community members. Risk factors that can be used as predictors of aggression in psychiatric patients include: factors related to the patient (e.g., gender, age, diagnosis, severity of psychopathology, addictions, history of violent behavior), factors related to the psychiatric institution (e.g., location, atmosphere, overcrowding, restrictions), and factors related to staff (average age and gender of medical staff, years of experience, quality of interaction with patients). The risk of aggression is higher in younger patients, males, those with lower education levels, addicts (especially if they use multiple substances simultaneously), and those forcibly detained in the institution, patients who have been previously hospitalized multiple times, have a history of violent behavior towards themselves or others, and those diagnosed with schizophrenia spectrum disorders (especially if psychotic). Risk assessment for aggressive outbursts is an important step in approaching a psychiatric patient. Assessment is conducted using numerous scales for evaluation. Actuarial instruments study static (unchangeable) risk factors, while structured professional judgment instruments are based on dynamic (changeable) factors. In general, it is desirable to approach a psychiatric patient with a combination of methods, i.e., pharmacological therapy combined with psychotherapeutic support. Clozapine is an atypical antipsychotic that reduces hostility, impulsivity, and aggressiveness in psychotic patients. The percentage of those whose clinical condition does not improve even after two different antipsychotics reaches up to 30%, and for them, clozapine is the solution. Drug side effects present a significant barrier to treatment, from non-adherence to therapy to discontinuation of treatment. Typical antipsychotics are characterized by extrapyramidal symptoms, for example, tardive dyskinesia. Other common side effects are anticholinergic effects, sedation, hyperprolactinemia, and orthostatic hypotension. Atypical antipsychotics cause metabolic changes—hyperglycemia, hyperlipidemia, and weight gain. The sedative effect varies from drug to drug. Clozapine stands out with specific side effects—neutropenia, i.e., agranulocytosis, and convulsions. Cognitive-behavioral therapy (CBT) has proven to be a good complement to medication therapy. Healthy lifestyle programs, socialization and employment programs, and securing housing, which raise the quality of life for psychiatric patients and give them a chance for a relatively normal life in the community, should not be neglected either.