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Student: Jasmine Gooda
Supervisors: Associate Professor Dee Mangin; Lead Clinical Facilitator Andrea Copeland
Sponsor: Pegasus Health

Anxiety and insomnia (difficulty sleeping) are very common conditions that affect around 1 million New Zealanders nationwide. There are many different medications used to treat these conditions - one such medication is quetiapine. Until recently, quetiapine was a restricted medication used in high doses (over 300mg daily) to treat mental health conditions such as bipolar disorder, mania, and schizophrenia. Some self-reported evidence suggests quetiapine can improve anxiety and insomnia in some people if given in regular low doses (up to 50mg daily). High doses of this medication are known to cause side effects such as weight gain, and altered blood sugar and cholesterol levels. However, there has been little research into whether low dose quetiapine also causes these side effects.


The aim of this pilot study is to find whether there has been any change in weight, blood sugar (glucose) and cholesterol levels while patients have been on a consistent low dose of quetiapine.


Source population: Patients of 16 Pegasus Health General Practitioners taking between 25-50mg of quetiapine daily.

Sample population: Patients from the source population who agree to take part in this pilot study. Database queries were run to find all patients fitting the study criteria. Any relevant information such as weight, body mass index (BMI), and blood glucose and cholesterol levels were noted.

Fifty six patients were found to fit the study criteria. These patients were sent a questionnaire asking if they had noticed any weight change since they started taking quetiapine. Their current height and weight, and other details related to weight change were entered into a database and simple statistic calculations were applied.


Thirteen of 56 patients responded to the questionnaire (a response rate of 23%). Eleven of these 13 patients reported a change in weight. Of these, 10 patients (76.9%) reported their weight had increased since starting quetiapine. If it is assumed patients who did not respond did not have a weight change, then of all patients sent a questionnaire 17.9% (10 out of 56) had gained weight.

The average current weight was 80.7kg, based on those who knew their current weight (12 out of 13). The average weight increase was 9.4 kg, based on the 9 out of 10 patients who knew their weight change.

Out of the 10 patients who reported weight gain, 7 knew their current weight and by how much their weight had increased. Six of these 7 patients also knew their height. This allowed for calculations of body mass index (BMI) changes. BMI is a ratio of weight to height and is classified into ranges that are associated with health risk.

The range for each BMI (in kg/m2) category is:

  • Underweight: less than 18.5
  • Normal weight: 18.5-24.9
  • Overweight: 25-29.9
  • Obese: 30-30+

The average known BMI of patients before starting quetiapine was 26.43 kg/m2. This means, on average 6 of the 13 patients who responded to the questionnaire were overweight before starting quetiapine. The average known BMI after starting quetiapine was 30.46kg/m2. This means, on average 6 of the 13 patients became obese whilst taking quetiapine.

The weight increases seen in the study are significant. Some patients may put on enough weight to change them from being normal weight to being overweight, or from being overweight to obese. This change in BMI is important as being overweight or obese increases health risks such as heart disease and diabetes.

The most common reason patients gave for their weight gain was quetiapine use (80% of patients). The second most common reason given was change in eating habit (50% of patients). These results overlap as each patient could tick more than one answer.

Just over half of the patients (53%; 7 out of 13) who responded had a change in appetite. Of these, 4 patients reported increased appetite. Overall, 7% (4 out of 56) of all patients sent a questionnaire reported increased appetite (even assuming patients who did not respond did not have a change in appetite).

As this is a pilot study, the number of patients selected and the number of questionnaires returned are small. Therefore, this study can only detect a signal for further research rather than providing a definitive answer. This study relied on patients' memory and recall, and there were factors other than quetiapine that may have influenced weight gain.


This pilot study showed that patients taking quetiapine who responded to the questionnaire had a clinically significant weight increase. Although this study was small and did not take confounding factors into account, an average weight increase of 9.4kg is large. Even if patients who did not respond had no weight change, this still shows at least 17.9% of the sample population gained weight. This is a strong signal that larger studies of people taking low dose quetiapine are needed to better see the adverse effects.

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