Obsessive-compulsive disorder (OCD) is a complex condition not solely caused by the lack of a single hormone or neurotransmitter, and the idea of a simple "chemical imbalance" is considered outdated. However, research strongly implicates dysregulation in the serotonin system and an imbalance in certain hormones.
Estrogen plays a role in augmenting feelings of anxiety, so high levels of estrogen can increase or lead to the development of OCD symptoms. Conversely, progesterone tends to inhibit anxiety, so a deficiency in that might lead to similar effects on OCD symptomatology.
There isn't one single "hardest" OCD, but treatment-resistant OCD (when standard therapies like Exposure and Response Prevention (ERP) fail) and types with deeply distressing, taboo themes like Harm OCD, Sexual Orientation OCD (SO-OCD), and Primarily Obsessional OCD (PO-OCD) are often considered among the most challenging due to their intensity, shame, and disruption to life. These often involve intrusive thoughts of violence, forbidden sexual acts, or religious blasphemy, leading to severe anxiety and difficulty engaging in treatment, with severe cases sometimes requiring advanced interventions like TMS, DBS, or residential care.
The idea that "chemical imbalances" are the only cause of OCD is outdated and too simplistic. However, an imbalance in neurotransmitters can play a role in OCD, with strong evidence that serotonin is implicated,.
Specific causes
People with OCD had increased risks due to lung diseases (73%), mental and behavioural disorders (58%), diseases of the urinary and reproductive organs (55%), endocrine, nutritional and metabolic diseases (47%), diseases of the blood vessels (33%), nervous system (21%) and digestive system (20%).
The 15-Minute Rule for OCD is a Cognitive Behavioral Therapy (CBT) technique where you delay performing a compulsion for 15 minutes when an obsessive thought triggers anxiety, allowing the urge to lessen naturally as you practice exposure and response prevention (ERP). It teaches your brain that discomfort decreases without the ritual, building resilience and breaking the obsessive-compulsive cycle by gradually increasing tolerance for uncertainty and distressing feelings.
Further studies show that earlier diagnosis and treatment lead to better long-term outcomes. For instance, untreated OCD can lead to significant issues, including relationship difficulties, struggles at work or school, and even the development of additional conditions like depression or anxiety.
Vitamin B12 deficiency is a commonly overlooked cause of psychiatric and even some neurological illnesses. Common neuropsychiatric illnesses associated with B12 deficiency are dementia, neuropathies, depression, and irritability. Authors concluded that OCD was an early manifestation of B12 deficiency.
Low serotonin symptoms often involve mood issues like depression and anxiety, sleep problems (insomnia), digestive troubles (constipation, appetite changes, carb cravings), and cognitive issues such as poor memory or focus, along with irritability and fatigue. These symptoms can also manifest as obsessive-compulsive behaviors, increased worry, difficulty managing emotions, and a general sense of unease or low well-being.
Dopamine levels are most depleted by chronic stress, poor sleep, lack of protein/nutrients, obesity, and excessive sugar/saturated fats, which desensitize receptors and impair production; substance misuse (like cocaine) and certain health conditions (like Parkinson's) also directly damage dopamine systems, reducing its availability. Unhealthy lifestyle habits, especially those involving processed foods and lack of sleep, significantly deplete this crucial neurotransmitter.
Leonardo DiCaprio lived with mild/moderate OCD for most of his adult life. He often feels the urge to walk through doorways multiple times.
Some theories suggest that OCD may be caused by something physical in our body or brain. These are sometimes called biological factors. Some biological theories suggest that a lack of the brain chemical serotonin may have a role in OCD.
AsianScientist (Mar. 26, 2025) – A group of researchers from South Korea has shown that a new non-invasive procedure, called magnetic resonance-guided focused ultrasound (MRgFUS) capsulotomy can potentially help in treating Obsessive-Compulsive Disorder (OCD).
Hormonal Fluctuations
Some studies suggest that estrogen has a protective effect on mood and cognition. Its decline can lead to increased emotional sensitivity and impaired stress response, which may create a fertile ground for OCD symptoms to surface or intensify.
Our results show that genetically based maternal effects contribute to offspring risk for OCD, and we conclude that such maternal effects contribute to a significant portion of the total genetic architecture of OCD, in addition to directly inherited, additive genetic effects.
Cortisol is the “stress hormone.” When it rises, it blocks insulin and pushes your blood sugar up. Overthinking keeps your cortisol levels high for too long.
A dopamine imbalance can cause depression symptoms, such as apathy and feelings of hopelessness, while a serotonin imbalance can affect the processing of emotions.
Serotonin is a chemical that the body produces naturally. It's needed for the nerve cells and brain to function. But too much serotonin causes signs and symptoms that can range from mild (shivering and diarrhea) to severe (muscle rigidity, fever and seizures).
You can try increasing your serotonin level by eating tryptophan-containing foods, such as:
Vitamin B12 and folate are thought to be effective in OCD treatment due to their associations with neurotransmitters. Depending on their antioxidant effect, zinc and selenium can be used in augmentation therapy for OCD. However, both trace elements and vitamin B12/folate can be affected by diet.
The 15-Minute Rule for OCD is a Cognitive Behavioral Therapy (CBT) technique where you delay performing a compulsion for 15 minutes when an obsessive thought triggers anxiety, allowing the urge to lessen naturally as you practice exposure and response prevention (ERP). It teaches your brain that discomfort decreases without the ritual, building resilience and breaking the obsessive-compulsive cycle by gradually increasing tolerance for uncertainty and distressing feelings.
Disorders That May Co-exist with OCD
OCD isolates the sufferer, and this detachment from others, where the person suffering from OCD is left alone with nothing but his or her obsessions and compulsions, can exacerbate OCD.
Can OCD lead to brain damage? OCD fundamentally changes the brain, showing a significant reduction in grey matter density in some regions. In severe cases, this can permanently change how the brain works for patients with OCD. However, most people can lead normal and happy lives with therapy and medication.
Severe OCD is also marked by compulsive behaviors or compulsive rituals that people do to try to ease anxiety. These can include excessive handwashing, checking and rechecking behaviors, counting, repeating words or phrases, or arranging objects in a specific manner.