Methamphetamine use continues to be a global public health concern: an estimated 30.5 million people worldwide used amphetamines (including methamphetamine) in 2023, according to the 2025 United Nations Office on Drugs and Crime (UNODC) [1]. In the UK, prevalence is much lower. According to the Crime Survey for England and Wales (year ending March 2024), 8.8% of adults aged 16–59 reported using illicit drugs, with 3.0% reporting Class A drug use—which in the UK includes methamphetamine [2]. While the survey does not disaggregate methamphetamine, it states that all other individual drug types not listed represent a prevalence of less than 1%, indicating that methamphetamine use is very rare in England and Wales [2]. The most detailed data available from the 2018–19 United Kingdom Drug Situation report estimated methamphetamine use at only ~0.03% of adults in England and Wales—approximately 11,000 individuals [3].

While community prevalence is low, treatment demand and acute harms have shown concerning trends. In 2018, 5.8% of new drug treatment cases in Wales were for amphetamine or methamphetamine, compared with 1.8% in England and 1.5% in Scotland [4]. Emergency department presentations involving methamphetamine in Central London increased dramatically—from just 4 cases in 2005 (1.9% of drug-related cases) to 294 cases in 2018 (16.2%) [5].

Despite low prevalence, methamphetamine-induced psychosis (MIP) remains clinically important. Up to 40% of users experience psychotic symptoms such as hallucinations, delusions, and paranoia, typically resolving after cessation [6]. However, some individuals experience persistent or recurrent psychosis lasting several months after chronic methamphetamine use [6]. Most literature focuses on psychosis following chronic, high-dose use, with limited documentation of prolonged psychosis after minimal exposure.

Chronic MIP can resemble primary psychotic disorders by inducing vivid visual and auditory hallucinations, strong delusions, and paranoid beliefs [7], complicating diagnosis and management. The phenomenological similarities include positive symptoms (hallucinations, delusions, disorganized behavior), negative symptoms (social withdrawal, blunted affect), and cognitive impairments, though the temporal relationship to substance use and response to abstinence can help differentiate MIP from primary psychotic disorders [8].

This case report explores the unusual course of residual psychosis in a woman who had very limited exposure to methamphetamine, highlighting the role of vulnerability factors and the need for early detection and comprehensive care.

A 53-year-old woman was referred to psychiatric services after her housing officer raised concerns. She had a background of anxiety, depression, and adult-diagnosed attention-deficit/hyperactivity disorder (ADHD). Her mood had been stable on sertraline (150 mg/day), and she took methylphenidate (Concerta XL 36 mg BD) for ADHD.

She initially presented with a six-month history of distressing visual hallucinations: seeing "white moths" and "mites" infesting her body, which she linked to chimney debris. She believed they had laid larvae inside her and contaminated her bloodstream. Despite repeated pest control visits confirming no infestation, she remained convinced, leading to obsessive cleaning, self-inflicted skin injuries, and food restriction.

Initial investigations in March 2024 were unremarkable. She initially denied any substance use and refused urine drug screening. However, later that month, she presented to the emergency department with acutely worsened psychotic symptoms (reporting moths emerging from her eyes) after using a larger quantity of methamphetamine than usual. A urine immunoassay screen at that time returned positive for amphetamines and benzodiazepines (prescribed). No confirmatory testing was performed. She then admitted to using methamphetamine ("Tina") by smoking, approximately once monthly with her partner, starting in September 2023. She reported that her psychotic symptoms began approximately one month after initiating use, in October 2023. She also disclosed historical cocaine use but stated she had ceased this several years prior; cocaine was not detected on toxicology screening.

She was started on risperidone 500 mcg twice daily, which was titrated to 1 mg twice daily. However, due to side effects including drowsiness and metabolic effects (weight gain), she was switched to aripiprazole 10 mg once daily. The patient was managed entirely in the community and was not admitted for inpatient treatment. She received intensive home treatment team support for two weeks following her emergency department presentation.

Despite abstaining from drug use since May 2024 and engaging with services, her symptoms—particularly persecutory delusions about her son—persisted. At times, she believed he had planted cameras and manipulated electronics using Artificial Intelligence, to the point where she would be frightened of chocolate wrappers or anything shiny, thinking they were cameras. These beliefs led to significant familial conflict, including estrangement and a police complaint. She ended her relationship with her partner (who had supplied the methamphetamine) in May 2024.

Sustained abstinence was confirmed through ten negative urine drug screens: five random tests by the home treatment team during the two-week intensive support period, two tests during home visits by her care coordinator in 2024, and three tests during psychiatry appointments (two after May 2024 and one in 2025). The patient did not undergo formal detoxification; she ceased methamphetamine use independently.

Over time, with consistent antipsychotic use and participation in cognitive behavioral therapy (CBT) for psychosis (21+ sessions beginning in November 2024), her insight improved. Notably, her insight regarding the connection between methamphetamine use and her initial symptoms developed early, after the positive urine test and psychoeducation about MIP during her psychiatry appointment in April 2024, she acknowledged the temporal relationship between drug use and symptom onset. However, her persecutory delusions about surveillance by her son were more resistant to treatment. She began questioning these beliefs in December 2024, gradually improving over subsequent months. By January 2025, she reported significant emotional recovery, 18 months after the onset of psychotic symptoms. She reconciled with her son, regained social support, and began volunteering. The timeline of the patient's journey, including symptom progression and recovery, is summarized in Table 1.

As of June 2025, the patient exhibits no psychotic symptoms and presents as euthymic, demonstrating strong engagement with her care team. A dose reduction of aripiprazole is planned, aligning with the patient's expressed wishes and observed clinical recovery. The patient maintains abstinence from illicit substances and alcohol, with all urine drug screens remaining negative.

This case highlights the complexity of MIP and how its course can defy clinical expectations. MIP is typically associated with high-dose or chronic use [6,7], but here, a woman with only occasional exposure (approximately eight smoking episodes over eight months) developed long-standing symptoms. The persistence of her symptoms—despite confirmed abstinence through multiple negative urine screens—mirrors descriptions of chronic MIP seen in other rare case reports [9]. One case report from Iran describes the diagnosis and treatment of a patient presenting with paranoid beliefs, auditory hallucinations, and low mood after chronic methamphetamine use [9]. That patient was also managed with antipsychotic medications such as risperidone and experienced persistent psychotic symptoms after abstinence from the drug during a one-year follow-up [9]. This illustrates the similarities between these patients' presentations and persistent symptoms despite their differing amounts of drug use, suggesting that individual vulnerability factors may be more important than dose or frequency in determining clinical course.

Several risk factors likely contributed to this prolonged psychosis. The patient had a history of ADHD (treated with methylphenidate), which is associated with increased vulnerability to psychosis following stimulant exposure [10]. Individuals with ADHD may have pre-existing dopaminergic dysregulation, and additional stimulant exposure from methamphetamine may precipitate psychosis more readily [10]. Her family history of mental illness may also have played a role. The patient reported a history of undiagnosed mental health conditions on both the maternal and paternal sides of her family, describing extreme mood fluctuations seen in several family members including her mother and father. This suggests possible genetic vulnerability to psychiatric disorders. Moreover, she had limited insight initially, was socially isolated, and relied on a single collateral informant. Loneliness and social isolation is a major risk factor in developing chronic psychosis, which has been recognized in clinical practice [11]. A meta-analytical review found a moderate positive association between loneliness and both positive and negative symptoms of psychosis, with loneliness potentially contributing to symptom persistence [11].

Identification of drug use was delayed by approximately one month since the first presentation because of the patient's reluctance, but with the establishment of a good rapport and support from mental health services, the patient eventually agreed to undergo drug analysis. Early toxicology screening is essential in such cases, especially when patients may be reluctant to disclose substance use [12]. The use of immunoassay screening in this case was appropriate for initial detection, though confirmatory testing would have provided additional certainty.

Treatment of chronic MIP remains challenging. While antipsychotics are often prescribed, evidence of their long-term efficacy is limited [6]. In this case, a combination of antipsychotic treatment and CBT for psychosis led to gradual recovery. The patient's early insight into the connection between methamphetamine use and her symptoms (developed after psychoeducation in April 2024) likely facilitated engagement with treatment and sustained abstinence. However, her persecutory delusions about her son were more treatment-resistant, only beginning to resolve eight months later in December 2024. This differential response suggests that while drug-related insight can be achieved relatively quickly through psychoeducation, delusional beliefs may require prolonged psychological intervention to fully resolve.

CBT has shown promise in helping individuals manage residual symptoms and avoid relapse, especially when focused on improving coping skills and promoting abstinence [13]. In this case, CBT appeared to play a crucial role in addressing the persistent persecutory delusions that remained after the patient achieved abstinence. While it is difficult to definitively separate the effects of pharmacological and psychological interventions in clinical practice, the temporal pattern suggests that antipsychotics provided initial symptom stabilization, while CBT facilitated the more gradual process of insight development and delusional belief modification. The extended duration of psychotic symptoms (18 months) despite early abstinence and antipsychotic treatment highlights the importance of combined pharmacological and psychological approaches in managing complex presentations of MIP.

This case also illustrates the broader biopsychosocial impact of MIP. The patient experienced job loss, family strain, and financial hardship, which outlasted the period of active psychosis. It emphasizes the need for integrated support that addresses not just psychiatric symptoms, but also social and functional recovery.

This case report has several limitations. First, only immunoassay urine screening was performed, without confirmatory testing such as gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS/MS). While the patient acknowledged methamphetamine use after the positive result, confirmatory testing would have provided greater diagnostic certainty and eliminated the possibility of false-positive results from cross-reactivity. Second, the patient disclosed occasional cocaine use in the years prior to presentation, though this was not detected on toxicology screening, and she reported cessation several years before. The potential contribution of previous stimulant exposure to her vulnerability cannot be fully excluded. Third, the exact timing and quantity of her final methamphetamine use prior to the positive urine screen is uncertain, as she presented to the emergency department after using a larger amount than usual but did not provide precise details. Fourth, there is limited literature on the consequences of minimal methamphetamine use compared to chronic use, making it difficult to contextualize this case within existing evidence. Finally, as a single case report, the findings may not be generalizable to other patients with MIP, particularly given the patient's multiple vulnerability factors, including ADHD, family history of mental illness, and social isolation.

This case challenges the assumption that methamphetamine-induced psychosis is a short-lived condition and that symptoms are dose-dependent with infrequent use. Even limited exposure (approximately eight smoking episodes over eight months) can be associated with persistent symptoms lasting 18 months, especially in individuals with pre-existing vulnerabilities such as ADHD, family history of mental illness, and social isolation. Clinicians should take a thorough drug history, remain alert to subtle signs of psychosis, and use early screening tools. This report illustrates the clinical significance of recognizing that individual vulnerability factors may be more predictive of prolonged psychosis than dose or frequency of use. Furthermore, it demonstrates how compassionate, flexible, and sustained treatment—including both pharmacological and psychological support—is essential to help patients recover and rebuild their lives. The differential response to treatment, with early insight into drug-related symptoms but delayed resolution of persecutory delusions, underscores the value of combined interventions addressing both acute stabilization and longer-term cognitive and behavioral change.