Many people have had the experience of a familiar smell bringing up a memory or a feeling. That is just one of several ways our sense of smell is associated with mental health and emotions.

Memories associated with a specific odor may be particularly strong. Odor memory is “long thought to be different than other types of memories, such as verbal or visual memories, being more strongly engraved and more closely related to strong emotions,” note researchers Judith Daniels, Ph.D. and Eric Vermetten M.D., Ph.D.(1) In writing about the relation of these odor-evoked memories to our mental health, psychologist Rachel Herz, Ph.D., concludes that “from numerous perspectives it is evident that the autobiographical memories and emotional associations that are triggered by odors are essential to our psychological and physiological health.”

The loss of sense of smell can have a significant impact on quality of life. For example, it can change how we experience and appreciate food and drink and increase potential risk from environmental hazards (such as fire/smoke or spoiled food).

Problems with our ability to identify smells are associated with several mental health conditions. Difficulties with sense of smell in individuals with schizophrenia are well-established. However, it is less understood how these problems with the sense of smell relate or contribute to other symptoms of schizophrenia. Some research has found a reduced sense of smell associated with feelings of depression and loneliness in older adults and with later development of dementia or Alzheimer’s.

A study involving a nationally representative sample of older adults without cognitive problems, assessed their ability to identify odors and then re-assessed them five years later. Those with greater problems identifying smells were at increased risk for dementia after five years, independent of other significant risk factors. The authors conclude that the odor identification test they used could be an efficient, low-cost component of physical exam that could provide useful information about an individual’s risk of dementia.

Another study looking specifically at the association of odor identification with Alzheimer’s disease similarly concluded that problems with odor identification may be a practical and affordable biomarker of Alzheimer’s. This early identification may provide an opportunity for early intervention to help reduce the challenges of dementia and Alzheimer’s.

Changes in a person’s sense of smell are also relatively common among people who have experienced a traumatic brain injury (TBI). An estimated one eight people with TBI experience a change in their sense of smell. Response to certain odors can be especially challenging for people with PTSD. Odors can trigger involuntary recall of emotional traumatic memories.

Odors that have positive memories and associations may also be beneficial for health and well-being. Odors evoking positive personal memories “have the potential to increase positive emotions, decrease negative mood states, disrupt cravings, and reduce physiological indices of stress, including systemic markers of inflammation,” according to recent review of research.