Scientists are reevaluating the causes of Alzheimer's beyond the amyloid hypothesis after numerous experimental drugs designed to target that theory have failed.

Recent evidence raises the question of whether conventional wisdom about amyloid plaques and their connection to Alzheimer's is wrong.

"Plaques" and "tangles" are top potential causes of Alzheimer's—but questions remain

The exact causes of Alzheimer's—and how to treat it—continue to be the subject of intense research. Two leading factors are amyloid beta plaques and tau protein tangles, which effectively pile up in the brain and interfere with neurons and cause cell death, which manifests as memory loss and other symptoms.

More than 200 drug trials for Alzheimer's have failed or been abandoned since 2010

The complexity of Alzheimer's disease, coupled with decades of underfunded research efforts, has left patients with little in the way of effective treatments. In recent years, scientists have synthesized several drugs that studies show can slow the progression of Alzheimer's—though the disease itself remains incurable.

Alzheimer's can cause brain shrinkage of between 10% and 30%

While the exact cause of Alzheimer's is debated, the buildup of amyloid plaques and tau protein tangles is instantly recognizable in post-mortem examinations. The atrophy of brain cells caused by this molecular pileup leads to noticeable physical changes, including significant shrinkage in affected brain regions.

Early-onset Alzheimer's can appear as early as age 30

Drugs recently approved to slow the progression of Alzheimer's appear to work best when administered as early as possible. Early stages are marked by a low buildup of tau, a protein experts believe clumps into misfolded, neuron-disrupting tangles once clusters of another protein—amyloid beta—have already started causing damage.

Visualize the difference between a healthy brain and one with Alzheimer's

The brain has three main parts—the cerebrum, brain stem, and cerebellum—each combining to control the entirety of the body's operations. Alzheimer's progressively deteriorates the circuitry in these structures, resulting in what we see as the symptoms of the disease.

Alzheimer's brain changes may begin years before symptoms appear.

There are two FDA-approved blood tests that may detect early Alzheimer's disease

Yet the tests are only recommended for those who have symptoms of dementia, and are not definitive on their own. False positives are a concern with these new tests, which detect biomarkers that may indicate the presence of brain proteins linked to the disease. This podcast explores the state of research on the disease and concerns about regulators taking jobs at pharmaceutical and biotech companies, which may influence their approach to approvals. It also dives into an investigation about the data underpinning one experimental Alzheimer's drug.

Alzheimer's disease is the leading cause of dementia and risks rise after age 65

Read this primer about Alzheimer's disease and learn what factors increase the risk of this form of dementia, including genetics, being a woman, and health conditions, including high blood pressure.

A top Alzheimer's researcher was accused of faking results

In 2021, an investigation revealed photo manipulation in images from a seminal 2006 paper by researcher Sylvain Lesné on the role of amyloid plaques in progressive Alzheimer's disease. The revelation rocked the field, leaving many wondering whether they had tried to build on fabricated results. (Some users may experience a paywall.)

How Alzheimer’s disease becomes fatal

Despite more than 100,000 people with Alzheimer's dying each year, the specific cause of death is not the disease itself. Often, secondary diseases arise from complications with the disease, including pneumonia, severe falls, malnutrition, or infection. Read more about the range of complications caused by Alzheimer’s here.

Multiple genes are associated with Alzheimer's risk, but one particularly well-known disease-associated gene is apolipoprotein E (APOE), which typically encodes a protein that helps carry cholesterol and other fats in the bloodstream.

Researchers are exploring neural links between Alzheimer's and autism

Recent DNA sequencing and molecular biology studies suggest that similarities in genes, neural circuitry and patterns of disease warrant further exploration to potentially better understand both conditions and how to treat them. (Some users may encounter a paywall.)

Chronic drug use can cause neurological changes in the brain

Neuroscientist Judy Grisel breaks down the biology of addiction, examining how drugs hijack the brain’s natural reward system and create lasting neural changes. The physiological and neurological impacts of chronic drug use require a multifaceted treatment approach.

Genetic blood test offers an estimated clock on when Alzheimer's symptoms may appear

The 2026 research finding from researchers at Washington University School of Medicine in St. Louis—if validated in broader populations—suggests that an already available blood test could estimate when Alzheimer's symptoms may begin within a margin of several years. The test detects a protein called p-tau217 found in blood plasma and the researchers incorporated the findings from that blood test into a statistical model to come up with the symptom timeline predictions.

Why genetic testing for Alzheimer's risk may not be right for you

Medical experts warn that completing Alzheimer's testing for late-onset versions of the disease can be fraught, in part because there's a shortage of genetic counselors to help navigate the findings and their potential implications, including for one's finances. Learning you have one or two copies of the APOE4 gene variant, which elevates Alzheimer's risk, can be panic-inducing, but an elevated risk for the disease is not the same as saying it definitely will develop.

Does our fear of Alzheimer's create stigma around its treatment?

Surveys suggest our fear of Alzheimer's as a disease outranks that of heart disease and cancer. This piece argues our fear of aging and the slipping away of our mental capacities make it more difficult to treat Alzheimer's compassionately.

Five to ten percent of Alzheimer's cases are early-onset

Early-onset Alzheimer’s typically emerges around 40 to 50 years of age, with devastating effects. This video follows Brian, diagnosed with the disease at age 54, as he travels the country as an advocate for research and discusses the progressive mental fog of Alzheimer’s.

The first identification of Alzheimer's was made in 1906

The first case of Alzheimer's disease dates to the early 20th century when Dr. Alois Alzheimer had 51-year-old Auguste Deter as a patient. Deter struggled with sudden memory issues and aggressive, irrational behavior. After Deter's death, Alzheimer examined her brain and found strange collections of molecular pileups.

Poor sleep increases the risk of developing Alzheimer's

Brain imaging studies reveal poor sleep leads to production of amyloid beta proteins—molecules linked to Alzheimer’s—which are cleaned from the brain during high-quality sleep. These findings suggest conditions like sleep apnea and insomnia increase the risk of developing the disease.

Alzheimer's in the United States is most prevalent in the South and the East.

How ALS (Lou Gehrig's Disease) might work, and what scientists are learning about it

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that affects the nerve cells (neurons) controlling muscle movement. As the motor neurons degenerate, they stop sending signals to the muscles, causing progressive muscle weakness and, eventually, death. This three-minute animation focuses on the mechanisms within the motor neurons that cause them to degenerate. By understanding these mechanisms, researchers hope to one day find a cure for ALS.

How depression affects the brain

Treatment for depression has historically hinged on the theory that the condition was caused by underactive or abnormal neurotransmitters, specifically serotonin and norepinephrine. This four-minute video by Yale Medicine details how these neurotransmitters didn't explain the symptoms of depression but, two other neurotransmitters involved in regulating mood and emotion did. GABA and glutamate, some of the brain's most plentiful neurotransmitters, may possibly be the source of depressive symptoms.

1440: Everything you need to know about Alzheimer's

What is Alzheimer's, and is it different from dementia? In short, yes—Alzheimer's is a specific brain disease that falls under the umbrella of dementia. However it is the most prevalent form of the condition, accounting for 60 to 80% of reported dementia cases.

MS Drugs reduce inflammation, helping reduce relapses and slow disease progression

Disease-Modifying Drugs calm the body's inflammatory response to help stave off relapses—when new or existing MS symptoms show up for a day or longer. Avoiding smoking, exercising, reducing stress via mindfulness, checking for vitamin D deficiencies, drinking more water and eating well, all can slow disease progression. [The jury's still out on if HRT around the time of menopause may reduce dementia risk](https://www.thelancet.com/journals/lanhl/article/PIIS2666-7568(25)00122-9/fulltext) Estrogen can reduce inflammation and support neural growth in the brain, and some research has suggested that beginning hormone replacement therapy around menopause—versus later in life—reduces Alzheimer's disease risk. Still, a recent systematic review concluded that taking HRT didn't affect dementia risk, regardless of when women started taking it, so the science remains unsettled.

These areas of the brain are hard-hit in depression—but the changes are reversible

Depressed brains can have certain characteristic changes, including an overactive amygdala, reduced hippocampus size, and changes to the thalamus and neuromodulating chemicals in the brain.

Some dementia cases may be linked to microorganisms in the brain

Researchers now know that, much like the gut, the brain is home to an ecosystem of microorganisms—the brain microbiome. While this area of study is still new, some scientists believe 50% of bacteria-caused dementia cases could be treated. (Some users may encounter a paywall.)

How aging degrades neural functioning in the brain over time

Aging affects the brain perhaps more than any other organ in the body. Throughout life, the brain experiences radical shifts in the number of neurons, synaptic connections between neurons, and hormone levels that regulate our mood and processing.

Researchers use the brain's ability to edit memories to explore memory deletion

Scientists have successfully implanted false memories in mice after studying how the editing process works in the brain. Beyond potentially deleting memories in those with PTSD, upcoming research may allow clinicians to forecast the onset of neurodegenerative diseases.

How neurodegeneration happens, the underlying disease process of dementia

Dementia symptoms may vary between individuals, and may include mood changes, difficulty walking, speaking, and memory problems. It can progress over many years, occurring due to progressive damage to nerve cells in the brain. This degradation may happen for myriad reasons, and its triggers are under investigation.

Memory disorders disrupt the brain's ability to make, store, or recall memories

These disorders stem from reversible issues like vitamin deficiencies or irreversible causes such as stroke or dementia. Only one type of dementia—familial Alzheimer’s disease—is directly inherited and accounts for about 20% of Alzheimer’s cases.

Depression changes the brain, causing distinct structural alterations visible on brain scans, but effective treatment can eventually make a depressed brain resemble a healthy one.

Read the original 1907 paper on the first known Alzheimer's patient

Alzheimer's disease was first identified by Dr. Alois Alzheimer in 1901, following a postmortem brain examination of a patient experiencing memory loss and other symptoms. Alzheimer's original paper was largely lost until 1995, when an English translation was published in a medical journal.

See how antidepressants were discovered

The decadeslong journey to the three major types of antidepressants began with medications designed to treat other maladies. Watch to learn more about how attempts to treat tuberculosis and blood pressure disorders led to new insights about neural chemistry and mood.

Analysis finds dementia was rare in ancient Greece

Ancient medical texts seldom mention severe cognitive decline, suggesting that such conditions were uncommon. This scarcity is attributed to factors like shorter lifespans and active lifestyles, implying that modern environmental and lifestyle changes—along with longer life expectancy—contribute to the current prevalence of dementia.

Advanced drugs are closing in on cancer's deadliest mutations

The protein KRAS, mutated in many cancers, was deemed ‘undruggable’. Now scientists are hoping to save lives with a batch of new compounds that target it.

Aging is a complex biological process affecting our cells, tissues, and organs.

Dementia describes progressive memory issues that impact daily activities

Although Alzheimer's disease is sometimes thought of synonymously with dementia, there are multiple types of dementia, which manifest in memory loss and other symptoms that make it challenging to perform daily tasks. These types include Lewy Body dementia, vascular dementia, and frontotemporal dementia. Parkinson's disease is not a form of dementia, but this movement disorder can sometimes develop into issues with memory and a formal diagnosis of dementia.

JJ Schildkraut theorized depression is linked to brain chemical imbalances—in 1965

Schildkraut was one of the first to put forward this idea, which stemmed from lab animal research. A decade later, researchers published the first landmark paper on fluoxetine—better known by trade name Prozac—which increases serotonin levels in the brain.

American medical organizations rescind recognition of diagnosis cited in police custody deaths

American medical organizations have rescinded their recognition of a syndrome whose theory stemmed from discredited research. This article explores the history and implications of "excited delirium syndrome," a medical condition that can reportedly...

Based on its varied symptoms, scientists think that long COVID-19 is not a single disease, but rather a group of different conditions triggered by COVID-19 infection.

Brain training game creates long-lasting changes in the brain that may help protect against dementia

Findings published in 2026 that tracked more than 2,000 older adults, examining dementia onset and completion of cognitive speed training activities, provide some of the strongest evidence yet that cognitive training games can help protect against dementia. Participants who underwent speed training and received booster sessions had a 25% reduction in the risk of dementia diagnosis compared with the control group.

How alcohol rewires your brain

Alcohol doesn't just make you tipsy—it rewires your brain chemistry in real time. It slows your brain with GABA, spikes dopamine to make you feel unstoppable, and blocks glutamate so you can't form memories. That mix explains everything from slurred speech to blackouts … and brutal hangovers.

A vaccine against Epstein-Barr virus, researchers hypothesize, could potentially prevent MS

As many as a quarter of MS patients have antibodies in their blood that bind to both a central protein in Epstein-Barr virus and a protein made in the brain and spinal cord that—when attacked—leads to a breakdown of protective nerve fiber insulation. This suggests the immune system's primed to attack the nervous system after mounting a defense against Epstein-Barr.

Learn the differences between mild cognitive impairment and age-associated memory loss

Mild cognitive impairment is a condition in which people experience more thinking and memory problems than expected for their age. It's often associated with depression and anxiety. Daily routines, writing things down, and healthy lifestyle choices can help cope with the condition, but there's no cure. The condition elevates the risk of developing dementia and Alzheimer's.

Multiple new research paths may lead to slowing (or even reversing) aging

Aging has always been inevitable, but fasting, epigenetic reprogramming, and parabiosis seem to help people stay young. By studying centenarians, memory, and even the humble roundworm, scientists are looking for the genetic basis to live not just a long life, but a healthy one.

Antidepressants alone may fail to help an estimated one-third to one-half of depressed patients.

Anthropic's interpretability team discusses how AI models' thinking mimics biology

Just as humans engage in complex behaviors to survive and reproduce, teams of experts in neuroscience, virology, mathematics, and other disciplines argue that large language models develop complex mechanisms to achieve their goals. These mechanisms can be manipulated to assess how they modify outputs—much like stimulating individual neurons—to uncover how LLMs "think."

Scientists William Russell and Rex Burch proposed in 1959 that when it comes to animal testing, there should be 'three Rs'—replace animals wherever possible; reduce their numbers; refine how they're treated.

Schizophrenia is challenging to diagnose and treat

The disorder is diagnosed by a clinician who observes behaviors and medical history and may run additional tests to rule out other explanations for symptoms including physical injury or other mental health disorders. But, ultimately, it's largely a diagnosis of exclusion—since there is no definitive test for the disease. Antipsychotic medications can help control its symptoms for some patients, but there is no cure for schizophrenia.