Mental Side Effects of Weight Loss Medications

When people talk about GLP-1 side effects, they mostly focus on the physical — nausea or constipation. These symptoms are easy to track and feel.

But the mental experiences are often overlooked. Yet for many, those are the ones that matter most.

While researching the topic, I was surprised by how much mental side effects can vary from person to person, among people taking Tirzepatide (Zepbound, Mounjaro) or Semaglutide (Ozempic, Wegovy). It’s truly an exceptionally wide range. One person feels free, finally in control. Another feels flat, like joy got switched off.

These experiences are shaped by several factors — brain chemistry, personal history with food and underlying mental health.

Why Mental Side Effects Vary So Much?

Brain chemistry is one factor. We all have different baseline levels of dopamine and serotonin, and GLP-1s can affect both. For someone with low dopamine levels, the medication might offer a sense of uplift and focus. However, for someone already in a delicate emotional state, the drug might push them into a fog, exacerbating existing issues.

Second, history with food. People with binge eating disorder or food addiction often feel relief — like a lifelong battle just stopped. Others, especially those who used food for comfort or identity, feel disoriented when hunger fades. It’s not just about less food. It’s about losing a part of themselves.

Third, underlying mental health. Depression or anxiety doesn’t disappear when appetite does. Sometimes it gets worse. Sometimes it gets better. It depends on the person, the support, and how well the change fits their life.

Underlying mental health also plays a role. Depression or anxiety can worsen or improve with GLP-1 use. For some, the suppression of appetite can bring relief, but for others, it can amplify existing issues.

Common Mental Side Effects of GLP-1

Anhedonia

Some people describe a strange flatness. Food used to be a joy, a reward, a celebration. Now, it’s just… fuel. The excitement is gone. Not just for food, but sometimes for everything. Things that used to spark joy — going out, cooking, even hobbies — can start to feel muted. It’s like someone turned down the volume on pleasure. People say they feel less connected, less lit up inside. They’re not sad, exactly. Just numb. And that emotional dulling can be unsettling.

Insomnia

Sleep becomes slippery for some. People report trouble falling asleep, staying asleep, or waking up too early. They lie in bed, tired but wired, the mind refusing to settle. For others, the sleep they get feels lighter and less restorative. Some describe vivid dreams or restless nights that weren’t an issue before starting weight loss meds. When rest disappears, so does energy — and everything feels harder the next day. It’s a side effect that sneaks in and quietly drains resilience.

Anxiety or Irritability

While appetite shrinks, anxiety sometimes grows. People report feeling on edge —restless, jumpy, easily overwhelmed. Small problems feel big. They snap at loved ones, stew over minor things, or find themselves more reactive than usual. It’s not constant, but it’s there. For some, it’s tied to blood sugar dips or the stress of adjusting to new eating habits. For others, it comes out of nowhere. What was supposed to bring calm instead brings tension.

Depression

Many share stories of unexpected sadness. The pounds drop, but so does their mood. They thought losing weight would feel like freedom. But for some, it brings a hollow ache instead. They miss comfort food. They mourn the person they were — even if that person was struggling. Others report an unexplained heaviness, a fog that won’t lift. It’s hard to say if it’s chemical, emotional, or both. But it’s real. And for some, it’s the hardest part of the journey.

Keep in mind, GLP-1 drugs affect more than hunger. They touch how we think and feel. The more we understand that, the better we can use them.

Here’s a list of studies and articles on the mental side effects and cognitive impacts of GLP-1 receptor agonists. They offer insight into how these drugs affect mental health and cognition:

1. A qualitative study of the mental health outcomes in people being treated for obesity and type 2 diabetes with glucagon-like peptide-1 receptor agonists

• Link: PubMed

• Summary: Explores participants' experiences with GLP-1 receptor agonists, highlighting both positive mental health impacts and acceptance of negative side effects for long-term benefits.

2. An analysis on the role of glucagon-like peptide-1 receptor agonists in cognitive and mental health disorders

• Link: Semantic Scholar

• Summary: Reviews evidence on GLP-1RAs in neurological and psychiatric disorders, discussing their potential repurposing for cognitive and mental health conditions.

3. Glucagon-like peptide 1 (GLP-1) receptor agonists in experimental Alzheimer’s disease models: a systematic review and meta-analysis of preclinical studies

• Link: PMC

• Summary: Evaluates neuroprotective effects of GLP-1RAs in Alzheimer’s disease models, showing improvements in learning, memory, and pathology markers.

Stay healthy (and hungry for knowledge),
Lucas Veritas