FILE PHOTO: Representation of Bitcoin cryptocurrency in this illustration taken September 10, 2025. REUTERS/Dado Ruvic/Illustration/File Photo

By Amanda Cooper

LONDON, Dec 1 (Reuters) - Bitcoin fell back below $90,000 on Monday, extending losses after its steepest monthly decline since the 2021 crypto crash, as renewed risk aversion drove investors out of stocks and digital assets.

The world’s largest cryptocurrency dropped 5% to $86,627, heading for its biggest one-day fall since early November and hovering near last month's eight-month low of $80,553.

Bitcoin shed more than $18,000 in November, its largest dollar loss since May 2021, when a number of cryptocurrencies collapsed.

Stocks in Europe fell in early trading, while U.S. futures pointed to a drop of 0.6-0.7% for the major indices later on, and safe havens such as gold and the Swiss franc edged up.

Given its relatively short lifespan, there is not much in the way of seasonality to guide traders' expectations for how bitcoin usually behaves in December.

On average, since its inception in 2012, bitcoin tends to rise by around 9.7% in December, ranking it third in terms of performance, with October being the strongest month, with an average gain of 16.6%, and with September, the weakest month, with an average loss of 3.5%.

Of more relevance might be bitcoin's tight correlation with the stock market at the moment, analysts said.

"Bitcoin tends to be a leading indicator for overall risk sentiment right now, and its slide does not bode well for stocks at the start of this month," XTB research director Kathleen Brooks said in a note.

"There is no obvious driver (on Monday), however, the sharp decline in volatility last week, the VIX fell back below the average for the last 12 months, may have unnerved some investors who remain concerned about an uncertain outlook into year-end," she said.

Ether, the second-largest cryptocurrency by market value behind bitcoin, was down 6% at $2,840, having lost some 22% in value in November, the most since February's 32% slide.

Since hitting a record of around $4.3 trillion in size, the entire crypto market has lost over $1 trillion in value, according to CoinGecko.

U.S.-listed exchange-traded funds backed by spot bitcoin witnessed record outflows of $3.43 billion in November, according to LSEG data. So far this year, a net $21 billion has flowed into these products.

(Reporting by Amanda Cooper; Editing by Louise Heavens)