Scientists can now see anxiety and depression by monitoring electrical signals in the brain, which could allow them to better diagnose and treat the mood disorders.
Both conditions are thought to be vastly under-diagnosed, and our methods of detecting them are highly subjective.
Without exact diagnostics, patients are left at the mercy of their doctors' interpretations of symptoms and may find themselves over-medicated or on a seemingly endless search for the right drug.
Scientists at the University of California, San Francisco think their new method of using electrodes to constantly track brain signals could some day change that, after it successfully identified anxiety in a small study of 21 epilepsy patients.
And the new method may someday allow doctors to use deep brain stimulation to treat mood disorders in a similar way that we can now care for Parkinson's patients.
If you are feeling under the weather, a doctor might chemically test a saliva culture for sign of the flu.
If your care provider thinks you could be diabetic, they can test your blood for insulin.
But if you think you might be depressed or suffer from chronic anxiety, you might be handed a survey to fill out about how you've been feeling, or your doctor might simply talk to you more.
In other words, long before you get answers, you have to answer more questions that are themselves rather ambiguous before getting diagnosed with either of the two most common mood disorders in the world.
And if you're one of the 17 percent of women and 28 percent of men in the US that don't have a primary care doctor, you may go years without even being asked the questions that could to a diagnosis.
More accurate and consistent screening has long been needed, and thought there are a few experimental techniques, nothing has been widely implemented.
Now, researchers at the University of California, San Francisco (UCSF), are throwing their hat in the proverbial ring.
In a small study, they decided to monitor the brains of 21 epilepsy patients for activity that might be connected to anxiety and depression.
Other studies have used functional MRI (fMRI) scans to monitor brain activity for a couple of hours at a time while the patient lies in the scanner.
But fMRIs don't measure brain signals directly, and establishing both a baseline and changes in activity and mood in such a short time is unlikely to give scientists the whole picture.
EEG electrodes, on the other hand, directly measure electrical activity in the brain.
The primary drawback to the EEG is simply inconvenience. Patients have to have electrodes placed on their heads, and these have to be monitored. For the most precise measures, however, electrodes are placed between the skull and the brain.
For the new study, the UCSF researchers had a sample of people who were going to be at the hospital - and would have to have open brain surgery regardless.
So the team recruited 21 epilepsy patients who were soon to have brain surgery to locate and diffuse the causes of their seizures.
To do so, they had to have electrodes placed inside their skulls any way, UCSF researchers decided to monitor them for both seizure and mood-related brain activity.
Prior to their operations - and the study - a number of the patients reported that they sometimes struggled with anxiety or depression.
Mood disorders and epilepsy share an underlying pattern in common. In both types of conditions, the brain's communication system goes a bit haywire.
In fact, in some epilepsy patients, depression symptoms can be one of the 'auras,' or warning signs that a seizure is on the horizon.
But that doesn't mean that the same brain regions are always involved in epilepsy and depression (or anxiety).
We do know that we process emotions in the amygdala and hippocampus. We are emotionally complex beings, and it isn't entirely clear what or how those two regions work to modulate mood, but we know that their communication is key to how we feel.
The UCSF researchers kept between 40 and 70 electrodes in the heads of their subjects for seven to 10 days, keeping constant track of brain waves that signal when brain regions are talking to each other - and how frantically they are 'speaking.'
'We were surprised to find such a clear and consistent signal, made up of interactions between the amygdala and hippocampus at a specific frequency, which matched changes in the mood seen in these 13 patients,' said co-senior study author Dr Vikaas Sohal.
'This study showed that there is a naturally occurring network that seems to consistently predict changes in mood among the majority of subjects.'
The same patients that reported anxiety or depression before the electrodes were placed showed the 'mood change' brain signal pattern.
'We are excited to find out how the communication between the amygdala and hippocampus, which are very near to each other, contributes to emotional processing and how this signal correlates with peoples' changes in mood state,' said the other co-lead author, Dr Edward Chang.
'This research is the first step in letting us look how the brain operates at different frequencies of brain activity, and it opens a lot of research and clinical questions.'
Of course, this first study was very small, and only 13 people showed the electrical activity the scientists said was indicative of mood changes.
So much larger studies will be needed to confirm the method, and it is - so far - quite invasive. But if it can be verified and simplified, the EEG system may tell patients once and for all whether their brains are behaving as they should, or not.